gemmi executable in a wheel

Here we provide the command-line program gemmi in wheels.

It is, in PyPI, distributed separately from the Python extension module gemmi, because, unlike the module, it does not depend on Python version.

notes for myself -- how to make wheels after gemmi release

• update GIT_TAG in CMakeLists.txt and version in pyproject.toml

• (optionally) update version of cibuildwheel in .github/workflows/wheels.yml and scikit-build-core in pyproject.toml

• test locally with pip wheel .

• make source distribution of this repo: python -m build --sdist

• git push changes to build wheels in GitHub Actions

• download the wheels, check them, upload sdist and wheels to PyPI:

  twine upload dist/gemmi_program-$VERSION.tar.gz
  twine upload wheels/gemmi_program-$VERSION-*.whl