Expand CODEOWNERS with more documentation DRIs

The @gitlab-bot often pings the whole @gl-docsteam for community contributions when it doesn't know who is the DRI for a page. It gets this information from the https://gitlab.com/gitlab-org/gitlab/-/blob/master/.gitlab/CODEOWNERS file, so we should expand this file with more detail to reduce the number of all-team pings.

For example, this is part of the first page of my recently cleared todos, almost all group pings, and upon review, none of the gl-docsteam pings were for any of my groups. 12+ people are pinged each time, but there is almost always one real DRI that could have been pinged directly (like the @marcel.amirault @sselhorn examples in the list below):

Screenshot

Proposal

• Use the metadata we have in all our docs to populate the CODEOWNERS file with the correct TW DRIs.