Smarter sorting

[friday]

The default sorting shows new extensions and there's a second one that sorts by github stars.
I think these are good to keep, but maybe adding a smarter one that combines factors to highlight both popular extensions and the well maintained ones.

For example, sorting by github stars, but adding a penalty for extensions based on how recent the latest commit was, if they have archived the repo, disabled the issue tracker etc.

(this is intentionally vague because I think it's hard to know what factors and how to weight them, until you sit down with it and try)