Add guide on mkdocs website dev

Author: Daniils Petrovs

DEVELOPMENT.md

@@ -26,3 +26,15 @@ Publish the draft release
 If you're debugging a running server than `IO.inspect` is a good approach, any messages you create with it will be sent to your LSP client as a log message
 
 To debug in tests you can use `IO.inspect(Process.whereis(:user), message, label: "message")` to send your output directly to the group leader of the test process.
+
+# Documentation website
+
+The documentation website is built using the [Mkdocs](https://www.mkdocs.org) static website generator. The content is written in Markdown format in the directory [docs](./docs) and is configured via the [mkdocs.yml](./mkdocs.yml) file.
+
+## Development
+
+Simply run `mkdocs serve` from the project root, this will start a local web server with a file watcher.
+
+## Build
+
+To compile the website for deployment, run `mkdocs build` from the project root. The built static assets will be located in the `site` directory. These can then be served by any web hosting solution.