Improve CI infrastructure for pre-commit by EliahKagan · Pull Request #2110 · gitpython-developers/GitPython

- Add `pre-commit` as an ecosystem for Dependabot version updates,
  now that it is available as a beta ecosystem. Enable beta
  ecosystems to allow this.

- Group the updates and use a monthly cadence to avoid getting
  swamped by frequent automated PRs.

- It would be valuable in the future to Use a 7-day cooldown period
  rather than taking new versions immediately once released. (This
  may also be of value to developers who use `pre-commit` locally.)
  However, this doesn't do that, since the Dependabot ecosystem for
  `pre-commit` does not currently support `cooldown`.

- Use a less busy style (less unnecessary quoting) than was being
  used in `dependabot.yml` before, since this new stanza is more
  elaborate than before. Apply that style to the existing stanzas
  for consistency.