Keep workflows active

Dieses Issue hat noch niemand übernommen.

Github will disable workflows for inactive projects, and a project goes inactive after 60 days with no commits.

This will stop smoke tests from detecting breaking changes from upstream package updates.

One solution (which I don't like, but I'm just leaving here to show there are automated solutions): https://github.com/marketplace/actions/keepalive-workflow

Alternatively, you have to pay attention to the github notifications and re-activate workflows each time you get an alert that they're being de-activated. From @DinoBektesevic:

> Every 60 days or so without a commit, you just have to go to the actions tab and press "Enable worfklow" again. The issue I have with the automatic disable isn't that it happens it's that the notifications are by default enabled just for the person that made the workflow - not all "admins" or "maintainers" of the repo. This is how sometimes these things go by unnoticed unfortunately because people don't subscribe or watch the action (which I don't think you can do). There's an email GA that can be used as a replacement I believe.

Beginne mit der Überprüfung der GitHub Actions-Workflows des Repositorys und der Smoke-Tests, die Breaking Changes durch Upstream-Paketaktualisierungen erkennen. Vergleiche den automatisierten Keepalive-Ansatz mit dem dokumentierten manuellen Reaktivierungsprozess und dem Benachrichtigungsverhalten. Als abgeschlossen sollte gelten, dass der gewählte Ansatz verhindert, dass die Workflows nach Zeiträumen ohne Commits stillschweigend deaktiviert werden.

Vom Indexierungsmodell aus dem Issue-Text verfasst.