Automate tagging a release every month with CI

[Lomanic]

We could have a CI job triggered every month or manually (just a click away) that would simply tag a release with git tag v2.$YEAR.$MONTH && git push origin v2.$YEAR.$MONTH if anything changed since the last tag.

This is linked to #734 (as in we should use the same CI service for both), but not exactly the same, though it would be better for it to be implemented on the same CI platform.

Not sure if it's feasible on a given CI platform tough, I know and used it with Gitlab, it looks possible with Github Actions.

What would you think of this idea @shirou? Would it be OK for it to be automatic without maintainers' intervention, each end of the month?

[Lomanic]

Closed with #1292