An image can be used by multiple containers and thus the loop will try
to remove the image from the list multiple times.

Check all containers (not just running) for images that are in use.

- Update the usage section.
- Add an explanation.

- Add a bunch of Python hooks.
- Update hooks.

Pretty much copy the new version of the .pre-commit-config.yaml
skeleton file.

Should be installable and the CLI should be there but do nothing.