Deduce the uid and gid from the volume owner and run as those. Don't
need to mount /etc/passwd and /etc/group inside the container (didn't
work with --user anyway). No hard-coded uids/ users anymore.

Don't use the host user home directory.

Install the version from my git fork which has a fix for a non-writable
config directory if the config file already exists.

This reverts commit fe7fdfb4. The image
is now available.

There aren't Alpine 3.13 tags for the Python image yet.

- More pre-commit hooks.
- Fixes from said hooks.
- pipenv updates.
- pre-commit updates.

The usage is completely replaced. Now locally I run inside a pipenv and
remotely using Docker.

- Use Supersonic as the Cron daemon.
- Run locally using pipenv.
- Run remotely using Docker (and docker-compose).
- Automate tasks using pipenv custom script shortcuts.
- Updated pre-commit hooks, added yamllint hook.
- Added license.
- Updated README.