Write commit message based on code changes with AI

I believe this is a feature that exists with Copilot in VSC too.

I'm also not convinced it's useful. Either the commit message contains surprising information that cannot be derived from the changes, or it doesn't and the message derivation can either be done in-real-time or by reading the changes manually. In general, I'd prefer the former state of things; the commit messages I find useful contain the "why", which often isn't clear from the code changes.