Create the `Gitlab/DocumentationLinks/Link` cop

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/165516



Merged-by: Peter Leitzen <pleitzen@gitlab.com>
Approved-by: Adie (she/her) <avpfestin@gitlab.com>
Approved-by: Peter Leitzen <pleitzen@gitlab.com>
Reviewed-by: Peter Leitzen <pleitzen@gitlab.com>
Reviewed-by: Paul Gascou-Vaillancourt <pgascouvaillancourt@gitlab.com>
Co-authored-by: Paul Gascou-Vaillancourt <paul.gascvail@gmail.com>
Co-authored-by: Paul Gascou-Vaillancourt <pgascouvaillancourt@gitlab.com>