feature: add avatar source

[tienhm0202]

• avatar can get via twenty-icons.com/. This website actually get domain favicon so it increase hit rate a lot.
• add logic to retry subdomain like mail.replit.com: if can not get favicon from subdomain, try getting from root domain.

[DamianB-BitFlipper]

Your change works like a charm! This should get merged in and a new release made. This fixes my issue: #19

Thanks for the work. Otherwise, I would have had to implement this ;)

[Striffly]

I will check this in mid-January, sorry for the wait. In the meantime, you can test the PR by following the "Build / Contribute" documentation.

[DamianB-BitFlipper]

Yes. I tested it this way. There are still some rough edges, though I am unsure if it is this PR's fault or the source code.

1. Still tries to load from clearbit despite the API being deprecated. This causes a lot of 404s in the console that are simply not needed.
2. When scrolling through the emails, it seems to constantly refetch icons. It would be good to have them cached.

@tienhm0202 Would you know?

[tienhm0202]

@DamianB-BitFlipper About the cache, I don't know how to improve. I 've just tried re-use logic of clearbit as much as I can, lol. I don't know the Clearbit is deprecated, just add a new avatar source as fallback by using twenty-icons.com.

May be @Striffly can help