Document priority of Pajamas usage

Marcel van Remmerdenrequested to merge
mvanremmerden-main-patch-33240 into main

What does this MR do?

Clarify that Pajamas content is primarily supposed to serve the GitLab product - GitLab.com, self-managed and dedicated instances - and document how teams that adopt it for other tools should think about how to use it.

Merge request reports