Implement support for git hooks

[pkage]

Added experimental support for git hooks as specially named tasks:

[scripts]

lint = "uvx ruff check"
git-hook-pre-commit = ["lint"]

Running ds with the --sync-git-hooks flag will discover a .git repository in your current repository (or parent repos) and install / update all hooks defined in your config into the .git/hooks/ directory. Arguments will be passed as normal to tasks.

This feature is experimental and opt-in, mostly because I can't figure out a good way to always keep the .git/hooks/ directory in sync with the task listing. The problem is that if you install a hook and then remove all hooks from the task listing: this looks identical to never having the hooks installed at all, and syncing the hooks stomps on all the installed hooks from other tools if you have them. I toyed with the idea of adding a separate config section for hooks specifically, but that ended up being awkward to implement with all the supported task config formats.

This branch ships with full unit tests and 100% code coverage (outside the pre-existing miss on runners.py 115-118), as well as docs/readmes.