Add GraphQL guide (#630)

* Including GraphQL API card

* GraphQL guide boilerplate

* GraphQL theme

* Introduction

* Running

* Crafting getting started section

* Adding images to the getting started

* Including server customize

* Your first query section

* Remove server customize session

* Adding objects section

* Object Create Generic Mutation section

* Class create mutation section

* Finding objects section

* Constraints, order and pagination sections

* Updating objects section

* Deleting an object section

* Users boilerplate

* Signing up section

* Logging out section

* Me query example

* Learning more section

* Update _includes/graphql/learning-more.md

Co-Authored-By: Tom Fox <[email protected]>

* Update _includes/graphql/users.md

Co-Authored-By: Tom Fox <[email protected]>

* Update _includes/graphql/users.md

Co-Authored-By: Tom Fox <[email protected]>

Author: TomWFox

_includes/graphql/getting-started.md

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+# Getting Started
+
+[GraphQL](https://graphql.org/), developed by Facebook, is an open-source data query and manipulation language for APIs. In addition to the traditional [REST API](/rest/guide/), Parse Server automatically generates a GraphQL API based on your current application schema.
+
+The easiest way to run the Parse GraphQL Server is using the CLI:
+
+```bash
+$ npm install -g parse-server mongodb-runner
+$ mongodb-runner start
+$ parse-server --appId APPLICATION_ID --masterKey MASTER_KEY --databaseURI mongodb://localhost/test --mountGraphQL --mountPlayground
+```
+
+Notes:
+* Run `parse-server --help` or refer to [Parse Server Options](https://parseplatform.org/parse-server/api/master/ParseServerOptions.html) for a complete list of Parse Server configuration options.
+* ⚠️ Please do not use `--mountPlayground` option in production as anyone could access your API Playground and read or change your application's data.
+
+After running the CLI command, you should have something like this in your terminal:
+
+<img alt="Parse GraphQL Server" data-echo="{{ '/assets/images/graphql/parse-graphql-server.png' | prepend: site.baseurl }}"/>
+
+Since you have already started your Parse GraphQL Server, you can now visit [http://localhost:1337/playground](http://localhost:1337/playground) in your web browser to start playing with your GraphQL API.
+
+<img alt="GraphQL Playground" data-echo="{{ '/assets/images/graphql/graphql-playground.png' | prepend: site.baseurl }}"/>

_includes/graphql/learning-more.md

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+# Learning More
+
+If you look at the right side of your GraphQL Playground, you will see the DOCS and SCHEMA menus. They are automatically generated by analyzing your application schema and contain all operations that you can call for your application, including the automatic class queries and mutations. Please refer to them and learn more about everything that you can do with your Parse GraphQL API.
+
+<img alt="GraphQL Docs" data-echo="{{ '/assets/images/graphql/graphql-docs.png' | prepend: site.baseurl }}"/>
+
+Additionally, the [GraphQL Learn Section](https://graphql.org/learn/) is a very good source to start learning about the power of the GraphQL language.