I have the exact same request as this guy , but I couldn't find a created issue for it.
I have quite a few projects belonging to a team account, with more being added. However a lot of documentation is more specific to the entire team rather than the different projects. The natural place to put this would be in a wiki tied to the team account.
Another option could be to assign a repository as the "team repository" so its README overview, wiki and issue tracker appears on the team profile page.
EDIT: A third option would be the option to make the team static site private so only team-members with read access can see it.