WIP: Add German translations from Transifex
This adds the German translations @teemo made in Transifex for https://gitlab.com/gitlab-org/gitlab-ce/issues/33312.
I'll keep these up-to-date, so we'd have the last work done there when our trial expires (mentioned in https://gitlab.com/gitlab-org/gitlab-ce/issues/33521#note_34854710)
This is based on https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13000 to have the linting of PO files.