Migrate to pyproject.toml

[paddatrapper]

Closes: #249

This seems to work on my system?

The upstream documentation can be found at:

• https://setuptools.pypa.io/en/latest/userguide/pyproject_config.html
• https://peps.python.org/pep-0621

[paddatrapper]

@alerque missed the GitHub Actions calls, should all be there now