[auth] Use website favicon as an icon backup.

[jacobhumston]

I'm not sure if this has already been suggested, however there are a few websites I use ente auth with that don't have an icon. (Mainly because they are not notable enough.)

My idea is that if the name of the auth matches a url pattern (such as example.com) then it will use the websites favicon as a backup icon if one is not already present.

This is really just a cosmetic suggestion that I thought might be interesting to think about.