Add MCP registry cheat sheet project link (modelcontextprotocol#600)

<!-- Provide a brief summary of your changes -->
Add the MCP registry cheat sheet project link in
`/docs/community-projects.md`

## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
It will be beneficial to have a cheat sheet that describes what are the
spaces of docs, organizes the spaces, and provides references to
detailed docs/guides/references. With such cheat sheet, new users would
quickly navigate in different spaces and find what commands and docs
they need.

More discussion at modelcontextprotocol#540 

## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->
No test needed.

## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [x] Documentation update

## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [x] I have added or updated documentation as needed

Author: subbyte

docs/community-projects.md

@@ -10,6 +10,7 @@ The following is a list of notable community-driven projects in the ecosystem re
 - [mcp-insights](https://github.com/joelverhagen/mcp-insights/) - Analytics and insights for the MCP Registry
 - [mcp-registry-spec-sdk](https://www.npmjs.com/package/mcp-registry-spec-sdk) - TypeScript client for the MCP Registry
 - [MCP Server for MCP Registry](https://github.com/formulahendry/mcp-server-mcp-registry) - MCP Server to discover and search for available MCP servers in the registry
+- [MCP Registry Cheat Sheet](https://github.com/subbyte/mcp-registry-cheatsheet) - MCP Registry Cheat Sheet for MCP server developers, client developers, and registry admin
 - Add your project here!
 
 ## Adding Your Project