Draft: feat: Add pre-commit hooks configuration

This adds a namcap and a namcap-system pre-commit hook.

The namcap hook is currently a bit cumbersome since it requires the user to get pyalpm installed into the Python virtual environment it’s running in, as it isn’t available in PyPI and setup.py doesn’t specify where to get it from. The namcap hook probably depends on #24 (ie., namcap needs to be installable with Python tooling).

namcap-system is a bit easier to handle since the user just needs namcap installed on their system.

Once/if merged, it can be used by downstream users with, e.g., a .pre-commit-config.yaml file like this:

repos:
- repo: https://gitlab.archlinux.org/pacman/namcap
  rev: 5c258eea3637348d9eee87af4f5edb835b21bb09
  hooks:
  - id: namcap-system