Updated CI config

[sveinbjornt]

• Only testing on CPython 3.9 and 3.13
• Explicitly supporting 3.13 in metadata
• Added testing on PyPy 3.10 (latest)
• Using uv for much faster CI runs

[Copilot]

Pull Request Overview

This PR updates the CI configuration to improve build speed and align supported Python versions with recent updates. Key changes include:

• Adding Python 3.13 to the supported classifiers in pyproject.toml.
• Updating the workflow matrix to test on Python 3.13 (and retaining Python 3.9 for PyPy) and upgrading the setup-python action from v4 to v5.
• Replacing multiple pip install commands with uv pip commands for faster CI runs.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
pyproject.toml	Added Python 3.13 classifier to indicate support.
.github/workflows/python-package.yml	Updated Python version matrix, upgraded setup-python action, and replaced pip with uv pip for installation.