Since we moved the Docker workflows to Github (after v1.10), they have
not been running on tags, so there are no tagged docker images for
v1.11, v1.12 and v1.13.
This is (hopefully) because we're not explicitly asking for the workflow
to be run on tag pushes.
This patch (hopefully) fixes that by adding an explicit section in the
config to make it run on tag pushes.
Thanks to Christoph Mewes (xrstf@github) for reporting this in
https://github.com/albertito/chasquid/issues/51.
We're running against the usage limits in Gitlab CI (500), and Github
Actions should have more (2000).
So this patch replaces Gitlab CI with Github actions for running
integration tests, and build and push Docker images (to Dockerhub and
Gitlab registry).
We'll see how the usage levels are in a few months.