CI: Build apk if a Merge Request was submitted
we can get some inspiration from https://gitlab.torproject.org/tpo/applications/fenix/-/blob/tor-browser-90.0.0b6-11.0-1/.gitlab-ci.yml
we can get some inspiration from https://gitlab.torproject.org/tpo/applications/fenix/-/blob/tor-browser-90.0.0b6-11.0-1/.gitlab-ci.yml