Run only documentation job if all changes are located in docs directory
Currently, we run the whle pipeline, even if only a typo in the documentation was fixed. It would be nice to just run the documentation job. Especially since changed to the documentation can be pushed more frequently, leading to oversubsription of our CI resources.
GitLabs rules should hopefully make this possible, though this may neccesitate the usage of yaml anchors, cmp: https://gitlab.com/gitlab-org/gitlab/-/issues/198688#note_437039708