Add more Git hooks, delegate to .local convention

The `pre-commit` and `prepare-commit-msg` git hooks can be used for some
interesting things such as linting files. For example:

https://github.com/croaky/dotfiles/commit/b3bc7d3f0dff46a47697c8c81a8352b76eb0e3a5
I was following the pattern used in the other `git_template/hooks/*` files. I think I'd like to leave it for that reason and open a separate PR to change all of them if we feel strongly.