checklist.rst

Procedure:

1. update release version/date in CHANGES.rst
2. create GitHub Release with new version tag, it will create a release on PyPI. tag MUST following semver. e.g.: 2.3.1
3. check PyPI page: https://pypi.org/p/sphinx-intl
4. prepareing for the next release: bump version in CHANGES.rst then commit/push it onto GitHub