Upstreaming meta data via AppStream

The following script allows automatically updating outdated information in the app files in content/apps/ based on AppStream metadata: https://framagit.org/linuxphoneapps/linuxphoneapps.frama.io/-/blob/main/checkers/check_via_appstream.py.

This massively decreases manual maintenance overhead and allows us to instead focus on adding additional value like testing the apps, storing mobile compatibility scores and so on.

In order for that workflow to work out, we need your help:

1. Make sure each repository has an AppStream metadata file. This job will list you the missing ones.
2. Add missing values: This job will show you where we have more information that reported upstream -> just search for "missing in upstream AppStream file. Consider contributing it upstream"