Migrate to pyproject.toml for packaging

[ericziethen]

• https://packaging.python.org/en/latest/guides/modernize-setup-py-project/
• https://packaging.python.org/en/latest/guides/writing-pyproject-toml/
• https://stackoverflow.com/questions/72018887/how-to-build-a-universal-wheel-with-pyproject-toml