add experimental get_latest_version tool

[juruen]

Context

This is an experimental feature that adds a new tool to check whether there's a newer version of the GitHub MCP server available.

The purpose of this PR is to gather feedback on whether we would like to have something like this. I see this as a moderately useful, but temporary, feature until this problem is solved by better means.

It exposes a tool that does the job by checking the latest available version of the GitHub MCP server to compare it against the current version.

Here's in action:

Note that we could tweak the response to point to the README, or a section in the README about updating.

[Copilot]

Pull Request Overview

This PR introduces an experimental tool to check if there is a newer version of the GitHub MCP server available.

• Adds a new get_latest_version tool in the server and exposes it in the server's tool list.
• Implements tests in pkg/github/server_test.go to validate version checking logic.
• Updates README.md to document the new tool.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
pkg/github/server_test.go	Adds tests to verify the functionality of the get_latest_version tool.
pkg/github/server.go	Implements the get_latest_version tool and integrates it into the server.
README.md	Updates documentation to include the get_latest_version tool.

Comments suppressed due to low confidence (1)

pkg/github/server.go:121

• The comment on line 121 incorrectly references 'getMe' instead of 'getLatestVersion'. Please update the comment to accurately describe the functionality of the get_latest_version tool.

// getMe creates a tool to get details of the authenticated user.

[SamMorrowDrums]

This is a really interesting idea! Love to know what @toby thinks of it too.

Sorry about renaming all the tools 😂

[pythonclcoding]

/describe