Cronberry

- License changed to GPL-3.0-or-later
- Pre-commit hooks updated
- License headers added as comments to RST files

Added CodeQL workflow to repository infrastructure. No functional changes were made since the last release.

Adds a `--version` option to the main `cronberry` command

- Updated examples in example script and README
- Updated docstrings for correctness

- Adds list command
- Fixes issue with writing shorthand syntax via `__str__()`
- Transforms Python exceptions to click.ClickException for CLI
- Removes unused sphinx configuration code