With the Toolbox container, I'm now on Python 3.9.

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.