Filter Site-admin > Users list by whether they are admins or not

Created by: dadlerj

We recently had a teammate depart, and when I went to disable their admin access on Sourcegraph.com, I faced an interesting challenge. Our user search only works for usernames (not emails), but even if it did, I'd have to guess whether the user in question's account was on their company email or a personal one.

It'd be great, for administrative security reasons, to be able to filter and see only admins on this page so they can be cleaned up if necessary.