checklist.rst

Procedure:

1. check GitHub Actions test results: https://github.com/sphinx-doc/sphinx-intl/actions
2. update release version/date in CHANGES.rst
3. python -m build, see details: setup.cfg
4. twine upload dist/<target-package-file>
5. check PyPI page: https://pypi.org/p/sphinx-intl
6. tagging with version name that MUST following semver. e.g.: git tag 1.0.1
7. git push --tags to push tag
8. bump version in sphinx_intl/__init__.py and CHANGES.rst then commit/push them onto GitHub