Use setuptools-scm for packge version handling

[Zeitsperre]

Description

This change makes two very small changes:

1. The package now implements setuptools-scm. What this now means is that versioning is entirely dependent on git tags and commits, i.e. commits that are tagged will show their version according to the tag (e.g. 0.0.27), while commits after this tag will have subsequent build history information (e.g. 0.0.27.dev66+g4e99390.d20250513). All of this is automated thanks to a new _version.py file which is ignored by git and generated on-the-fly when building or installing the package. In other words, no more need to manage versioning within the codebase. xskillscore.__version__ works almost exactly as before.
2. In my last PR, I forgot to modify the accel recipe. This now installs the relevant numba version and is used to compose the test recipe to reduce redundant configurations.

This PR also adds my contributor information.

If the maintainers wish it, I (or you) can update the release date.

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• Refactoring

How Has This Been Tested?

Locally tested using:

$ python -m build
$ python -m pip install -e .

Checklist (while developing)

N/A

Pre-Merge Checklist (final steps)

• I have rebased onto main or develop (wherever I am merging) and dealt with any conflicts.
• I have squashed commits to a reasonable amount, and force-pushed the squashed commits.

References

https://setuptools-scm.readthedocs.io/en/stable/usage/

[raybellwaves]

I'm not monitoring this repo anymore. Happy to give you merge permission if @aaronspring approves and you accept

[Zeitsperre]

@raybellwaves Sure, I don't plan on building out any new features, but seeing as my team uses xskillscore in our tech stack, being able to maintain it would be helpful. Thanks!