Switch to pyproject.toml and Hatch build

[oprypin]

Biggest remaining issues:

• I can't actually remove setup.py because we have commands that require it:
  E.g. python setup.py compile_catalog -t mkdocs

  • I can't set the license because during the above command, setuptools says:

    configuration error: `project.license` must be valid exactly by one definition (2 matches found):
    
        - keys:
            'file': {type: string}
          required: ['file']
        - keys:
            'text': {type: string}
          required: ['text']
    

[facelessuser]

• I can't actually remove setup.py because we have commands that require it:
  E.g. python setup.py compile_catalog -t mkdocs

What about something like this? https://github.com/facelessuser/Rummage/blob/master/pyproject.toml#L98

[oprypin]

Sigh, still really scared about losing the "Used by" section, but let's hope for the best

[ofek]

Success, it's still there 🙂

[oprypin]

For now, anyway 🙂