Conditional running of CI workflow jobs

When documentation-only changes are made to a PR, we currently let all the workflow jobs run. That uses a lot of resources.

Consider implementing conditional execution of workflows depending on what files changed in a commit. For example, if the only changes are in the changelog folders, then do not bother running unit and acceptance tests, just run the various commit format, PR title etc lint checks.

Possible GitHub action to do this:

https://github.com/dorny/paths-filter