Draft: Dependabot

replaces !2373 (closed) because the original branch name caused issues

Unfortunately this still doesn't work:

• I managed to create a pull request: !2412 (closed)
• I also managed to start this from a gitlab schedule
• I was not able to restrict the kinds of updates that are made. dependabot.yml seems to get ignored.
• npm dependencies are detected but not updated
• python dependencies are not even detected

I am close to giving up.