docs: add Gemini Docs MCP setup

[thisisryanswift]

Documentation update to include the Gemini Docs MCP server and a link back to the official docs.

Closes #33

[gemini-code-assist]

Code Review

This pull request updates the README.md to include a new section for the Gemini Docs MCP, providing installation instructions and links to additional documentation. The review feedback suggests using the term "tool" instead of "function" for consistency with MCP terminology, renaming a heading for better clarity, and formatting a bare URL as a Markdown link.

[thisisryanswift]

While working on this, I found that search_documentation has been renamed to search_docs. I’m including that correction in this PR since it's relevant

[markmcd]

Thanks - this is great. It looks good to me but I want @treyn-create to PTAL too.

I also made a few minor tweaks, mainly to align with the style guide (e.g.)

[treyn-create]

This LGTM. Thanks for contributing!