Add GitHub commit URL detection to show commit info instead of repo info

[mvineetmenon]

This change adds support for detecting GitHub commit URLs in the Cardinal IRC bot's GitHub plugin. When a commit URL is posted in a channel, the bot will now display the commit subject and add/delete statistics instead of the repository information.

Changes Made:

• Added COMMIT_URL_REGEX to match GitHub commit URLs with the pattern https://github.com/user/repo/commit/sha
• Modified the get_repo_info event handler to check for commit URLs first, prioritizing them over issue/repo URLs
• Added _show_commit method that fetches commit data from the GitHub API and formats it as sha: subject (+additions -deletions)
• Updated test suite to include comprehensive tests for commit URL detection and display functionality
• Removed extraneous tests to keep the implementation focused on the core commit URL feature

The implementation maintains backward compatibility - repo and issue URLs continue to work as before, but commit URLs now get special handling to show more relevant commit-specific information.

Test Plan

• Added unit tests for COMMIT_URL_REGEX pattern matching with various GitHub URL formats
• Added integration tests for get_repo_info method with commit URLs, including cases with and without commit stats
• Added test for issue URL handling to ensure existing functionality remains intact
• Added test for repo URL fallback behavior
• All tests use mocked HTTP responses to avoid external API dependencies
• Tests verify correct message formatting and API call patterns
• Ran existing test suite to ensure no regressions in other plugin functionality

Contribution Checklist

• I have read the contributing guidelines.
• I consent to the MIT project license.
• I have added my name to the CONTRIBUTORS file if desired (optional).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.77%. Comparing base (f74b0ec) to head (e7162c2).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #213   +/-   ##
=======================================
  Coverage   88.77%   88.77%           
=======================================
  Files           8        8           
  Lines        1042     1042           
=======================================
  Hits          925      925           
  Misses        117      117           

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[johnmaguire]

Hey this looks really great, thank you for this! I will test it out soon and merge it as long as everything is working correctly.

One quick thought - Github often uses this syntax for identifying issues: #213. Perhaps it's worth supporting this format in the .issue command? Totally irrelevant to the current PR, ignore me please.