Resolve "Update developing plugin documentation"
Further updates to plugins docs.
We’ve updated our runner tagging system. If you’re using our shared runners for your CI pipelines, please review the new tags here: https://docs.mpcdf.mpg.de/bnb/220.html#new-tags-for-mpcdf-gitlab-runners
The old tags will remain valid until the end of February 2026.
Further updates to plugins docs.