docs: create contribution guide

CONTRIBUTING.md

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+# Contributing
+
+When contributing to this repository, please first discuss the change you wish
+to make via issue, pull request, or any other method with the owners of this
+repository before making a change.
+
+Please follow the [code of conduct][code-of-conduct] in all your interactions with the project.
+
+## Developer Startup Guide
+
+This section will walk you through how to get started working with the code.
+
+### Runtime
+
+We recommend you install Node Version Manager for [UNIX systems][nvm-unix] or [Windows][nvm-windows].
+
+All code changes must work on the minimum Node version specified in [package.json](./package.json) under the "engines" key.
+
+### Get the Code
+
+Begin by creating a fork of this repo and cloning the fork.  Then run `npm install` to install necessary dependencies.
+
+### Visual Studio Code Setup
+
+One option to get up and running quickly is to use a preconfigured VS Code [workspace][workspace-file].  Save the the workspace file in a directory separate from the directory where you cloned this repo.  Open the workspace file in VS Code, and update `folders.path` to point to your local `js-bson` directory and update the `runtimeExecutable` field of the launch configuration to be the path to your Node.js executable.
+
+Alternatively, if you just want to get formatting and linting working automatically, add these settings to your VS Code code workspace:
+
+```jsonc
+"settings":{
+  "editor.codeActionsOnSave": {
+    "source.fixAll.eslint": true
+  },
+  "[javascript]": {
+    "editor.defaultFormatter": "dbaeumer.vscode-eslint"
+  },
+  "[typescript]": {
+    "editor.defaultFormatter": "dbaeumer.vscode-eslint",
+  }
+}
+```
+
+We recommended these VS Code extensions:
+  - [eslint](https://marketplace.visualstudio.com/items?itemName=dbaeumer.vscode-eslint)
+  - [test-explorer](https://marketplace.visualstudio.com/items?itemName=hbenl.vscode-test-explorer)
+  - [mocha-test-adapter](https://marketplace.visualstudio.com/items?itemName=hbenl.vscode-mocha-test-adapter)
+  - [coverage-gutters](https://marketplace.visualstudio.com/items?itemName=ryanluker.vscode-coverage-gutters)
+  - [pull-request-github](https://marketplace.visualstudio.com/items?itemName=github.vscode-pull-request-github)
+  - [mongodb](https://marketplace.visualstudio.com/items?itemName=mongodb.mongodb-vscode)
+  - [gitlens](https://marketplace.visualstudio.com/items?itemName=eamodio.gitlens)
+
+
+### Automated Tests
+
+This repo contains a suite of automated tests that can be run with the following command:
+
+```bash
+npm run test
+```
+
+### BSON benchmarking
+
+The `test/bench` directory contains the files pertinent to performance testing of js-bson.
+
+The `test/bench/documents` directory contains generated documents used for performance testing
+
+The `test/bench/etc` directory contains scripts used to run benchmarks, generate benchmark documents and
+process the results.
+
+The `test/bench/granular` directory contains files that test bson performance in a range of different
+scenarios using the bson-bench library.
+
+The `test/bench/spec` directory contains one file used to run the performance tests mandated by the bson
+[microbenchmarking](https://github.com/mongodb/specifications/blob/master/source/benchmarking/benchmarking.md#bson-micro-benchmarks) specification.
+
+
+Granular tests can be run from the repository root by running:
+
+```bash
+WARMUP=<warmup iterations> ITERATIONS=<measured iterations> npm run check:granular-bench
+```
+
+This will build the granular tests and run them with `test/bench/etc/run_granular_benchmarks.js`. The `WARMUP` and `ITERATIONS` environment variables can be optionally provided to configure how these granular benchmarks
+are run. `WARMUP` changes the number of iterations run before results are collected to give v8's
+optimizing compiler time to reach steady state. `ITERATIONS` changes the number of iterations that
+are measured and used to calculate summary statistics. Note also that the test can be configured to
+make use of the local copy of bson when testing performance changes locally by setting the `LIBRARY`
+variable to the root directory of the bson library to be tested.
+
+```bash
+WARMUP=100 ITERATIONS=1000 LIBRARY=$(pwd) npm run check:granular-bench
+```
+When the `LIBRARY` environment variable is unset, the benchmark clones and runs against the main
+branch of this repository.
+
+When the script is complete, results will be output to `test/bench/etc/resultsCollectedMeans.json`. These results will
+be in a format compatible with evergreen's perf.send command. To convert these results to CSV, run
+the following command from the repository root:
+
+```bash
+./test/bench/etc/convertToCSV.js < test/bench/etc/resultsCollectedMeans.json > resultsCollected.csv
+```
+
+Spec tests can be run from the repository root by running:
+
+``` bash
+npm run check:spec-bench
+```
+
+This will run the spec benchmarks in `test/bench/spec/bsonBench.ts` which also makes use of the
+`bson-bench` library. Results will be written to `bsonBench`. The warmup and iterations are not
+configurable as these are determined by the common driver benchmarking specification, but similar
+to the granular benchmarks, the spec benchmarks can be run against the local copy of bson by setting
+the `LIBRARY` environment variable appropriately.
+
+```bash
+LIBRARY=$(pwd) npm run check:spec-bench
+```
+
+### Commit messages
+
+Please follow the [Conventional Commits specification][conventional-commit-style].
+The format should look something like the following (note the blank lines):
+
+```txt
+<type>(<scope>): <subject>
+
+<body>
+```
+
+If there is a relevant [NODE Jira ticket][node-jira], reference the ticket number in the scope portion of the commit.
+
+Note that a BREAKING CHANGE commit should include an exclamation mark after the scope, for example:
+
+```text
+feat(NODE-xxxx)!: created new version api, removed support for old version
+```
+
+This helps the team automate [HISTORY.md](HISTORY.md) generation.
+These are the commit types we make use of:
+
+- **feat:** A new feature or deprecating (not removing) an existing feature
+- **fix:** A bug fix
+- **docs:** Documentation only changes
+- **style:** Changes that do not affect the meaning of the code (e.g, formatting)
+- **refactor:** A code change that neither fixes a bug nor adds a feature
+- **perf:** A code change that improves performance
+- **test:** Adds missing or corrects existing test(s)
+- **chore:** Changes to the build process or auxiliary tools and libraries such as documentation generation
+
+## Conventions Guide
+
+Below are some conventions that aren't enforced by any of our tooling but we nonetheless do our best to adhere to:
+
+- **Disallow `export default` syntax**
+  - For our use case, it is best if all imports / exports remain named.
+- **As of 4.0 all code in src is in Typescript**
+  - Typescript provides a nice developer experience.
+    As a product of using TS, we should be using ES6 syntax features whenever possible.
+- **Errors**
+  - Error messages should be sentence case and have no periods at the end.
+
+## Pull Request Process
+
+1. Update the README.md or similar documentation with details of changes you
+   wish to make, if applicable.
+1. Add any appropriate tests.
+1. Make your code or other changes.
+1. Please adhere to the guidelines in [How to write the perfect pull request][github-perfect-pr], thanks!
+1. Please perform a self-review using the reviewer guidelines below prior to taking the PR out of draft state.
+
+### Reviewer Guidelines
+
+Reviewers should use the following questions to evaluate the implementation for correctness/completeness and ensure all housekeeping items have been addressed prior to merging the code.
+
+- Correctness/completeness
+  1. Do you fully understand the implementation? (Would you be comfortable explaining how this code works to someone else?)
+  1. Does the code meet the acceptance criteria?
+     - If there is an associated spec, does the code match the spec?
+  1. Is the intention of the code captured in relevant tests?
+     - Does the description of each test accurately represent the assertions?
+     - For any test explicitly called out on the ticket as desirable to implement, was it implemented?
+     - If there are prose spec tests, were they implemented?
+     - If there are associated automated spec tests, were they all pulled in and are they all running and correctly interpreting the spec inputs?
+       - Are any runner changes needed to process new input types?
+  1. Could these changes impact any adjacent functionality?
+  1. Are there any errors that might not be correctly caught or propagated?
+  1. Is there anything that could impact performance?
+  1. Are there any race conditions in the functional code or tests?
+  1. Can you think of a better way to implement any of the functional code or tests? "Better" means any combination of:
+     - more performant
+     - better organized / easier to understand / clearer separation of concerns
+     - easier to maintain (easier to change, harder to accidentally break)
+- Housekeeping
+  1. Does the title and description of the PR reference the correct Jira ticket and does it use the correct conventional commit type (e.g., fix, feat, test, breaking change etc)?
+     - If the change is breaking, ensure there is an exclamation mark after the scope (e.g., "fix(NODE-xxx)!: \<description\>" )
+  1. If there are new TODOs, has a related Jira ticket been created?
+  1. Are symbols correctly marked as internal or public?
+  1. Do the Typescript types match expected runtime usage? Are there tests for new or updated types?
+  1. Should any documentation be updated?
+     - Has the relevant internal documentation been updated as part of the PR?
+     - Have the external documentation requirements been captured in Jira?
+
+[conventional-commit-style]: https://www.conventionalcommits.org/en/v1.0.0/
+[code-of-conduct]: CODE_OF_CONDUCT.md
+[github-perfect-pr]: https://blog.github.com/2015-01-21-how-to-write-the-perfect-pull-request/
+[mdb-core-values]: https://www.mongodb.com/company/
+[nvm-windows]: https://github.com/coreybutler/nvm-windows#installation--upgrades
+[nvm-unix]: https://github.com/nvm-sh/nvm#install--update-script
+[workspace-file]: https://gist.github.com/W-A-James/5c1330f23ad9359b8b5398695ae2c321
+[node-jira]: https://jira.mongodb.org/browse/NODE