Modernize packaging and fix CI

[ngoldbaum]

Fixes #129

I think these days there's no need to have an optional dependency on Cython. You can declare cython as a build dependency in your pyproject.toml and pip or uv will install Cython in the build environment.

I make use of that capability to substantially simplify the setup.py file.

Since creating a pyproject.toml file automatically opts into pep 517 isolated builds, I also took the opportunity to move all the static metadata into pyproject.toml.

I probably also need to update the makefile and readme but I didn't want to do that without confirming that this approach is OK with the maintainers.

To get the CI to pass I also had to drop Python 3.8 support. Python 3.8 has been EOL since October 2024.

[tonybaloney]

3.9 per the changes

[zweizeichen]

While you're at it... (I know, sorry)

Would you mind adding Python 3.14 to the build so wheels for 3.14 get uploaded once this has been merged and released?

At this time there's only 3.13

[ngoldbaum]

Would you mind adding Python 3.14 to the build so wheels for 3.14 get uploaded once this has been merged and released?

Sure! I was planning to do that in a followup but I can do it here just as well.

I'll try to get this done this week but I'm traveling and may not have time until next week.

[ngoldbaum]

Sure! I was planning to do that in a followup but I can do it here just as well.

Actually, on second thought, I'll open a followup with this. I still haven't heard from a project maintainer on this PR and I'm not sure if they're OK with these changes.

[Carreau]

Hi, working with @ngoldbaum,

I've updated pyproject.toml to mention 3.9 and increase testing range to 3.14 (which I can also do in a separate PR)