appview: add pagination to stars page

Performance of the stars page for repos with many stars is pretty bad, with the page fetching avatars and triggering DID resolution for all users shown on the page (~820 for tangled.org/core for example). This PR adds pagination to only show 30 users per page, and also only resolve those DIDs and avatars. Sorry I didn't catch this when I implemented the stars page, I didn't have a test repo with enough stars to run into this (I also don't have enough test accounts)