switch to pyproject.toml, simplify requirements setup

[mathiasertl]

Another attempt to switch to pyproject.toml. I already did this before I found #174 - so I apologize for the duplication. Since I already did it, I thought I'd still make a PR, feel free to close if using that other PR:

Some notable changes to #174:

• Minimal build-system requires.
• Update authors, add maintainers
• more complete project URLs.
• Include setuptools configuration in pyproject.toml, where possible.
• setup.py is really minimal and also formatted using ruff already (this would be a different task for the whole project, of course).

[joseavegaa]

Still waiting for an update on this. The current state of the repo does not allow installation on Windows 11 with Python >3.11, at least with my testing in several new environments.

Hope one of the PR's gets merge soon.

[kislyuk]

LGTM, thanks!