Link to a succinct list categorizing the teams and project groups

[yaahc]

I got feedback that the question about "How are you associated with the Rust Project" might be confusing to some people because for some teams it's not particularly clear that they are in fact teams. The specific example was "Compiler Team Contributors", which is a subteam of the compiler team. This doesn't clearly appear to be a team in it's own right and isn't marked as one, though in the teams repo it is marked as a subteam and does not have a kind field indicating that it is a project group or working group.

To avoid this potential confusion we should create an easy to check list of the teams, project groups, and working groups. That way contributors who are unclear can open up the list and find the team/groups they're involved in and confidently select the correct answer.