[amannocci]

Small changes that make the project easier to find and evaluate on PyPI and GitHub.

Changes

• Metadata: declare macOS support, which CI already covers, and link the changelog from PyPI.
• Python versions: test and declare support for Python 3.14 and 3.15.
• README: replace the contributors badge with a no-dependencies badge.
• GitHub Releases: add a github-release job to release.yml. It runs after PyPI publishing and uses the version's changelog entries as the release notes, through a new release:github task.

Testing

• uv run poe ci passes on Python 3.12.
• The test suite passes on Python 3.14 and 3.15 on macOS. This PR's CI covers the other OS and version combinations.
• release:github was only run against a fake gh: it passes the expected arguments and notes for 0.1.0, and refuses a dev version or a version with no changelog entry. The real job first runs on the next release.