Add overview page for the CircleCI MCP server

[rosieyohannan]

Description

• Add overview page for using the mcp server
• Add page to the side nav under Developer Toolkit section
• Add required lint rules
• Add example screenshot showing Cursor settings

Reasons

Support release

Content Checklist

Please follow our style when contributing to CircleCI docs. Our style guide is here: https://circleci.com/docs/style/style-guide-overview.

Please take a moment to check through the following items when submitting your PR (this is just a guide so will not be relevant for all PRs) 😸:

• Break up walls of text by adding paragraph breaks.
• Consider if the content could benefit from more structure, such as lists or tables, to make it easier to consume.
• Keep the title between 20 and 70 characters.
• Consider whether the content would benefit from more subsections (h2-h6 headings) to make it easier to consume.
• Check all headings h1-h6 are in sentence case (only first letter is capitalized).
• Is there a "Next steps" section at the end of the page giving the reader a clear path to what to read next?
• Include relevant backlinks to other CircleCI docs/pages.

[stiyyagura0901]

Should we consider adding a "Troubleshooting" section to address common issues users might encounter.

eg:
Troubleshooting

• Updating Available Tools: After new tools are released, you may need to restart your MCP server to access them. Simply reload your IDE window to ensure the CircleCI MCP server loads the most recently released tools and capabilities.