Making a Release of pytest-mpl

To make a new release of pytest-mpl follow the following steps:

Ensure the sdist and wheel GitHub Actions jobs succeeded on main after the last merge.
Also ensure that the tarball built has an autogenerated version number from setuptools_scm.
Write the release notes in the GitHub releases UI, use the autogenerated notes and tidy up a little.
Publish the new release, using the format vX.Y.X.
Watch as GitHub actions builds the sdist and universal wheel and pushes them to PyPI for you, and updates CHANGES.md on the main branch.
Enjoy the beverage of your choosing 🍻.