Add nostr relay management

[sondreb]

Consider using this JSON to display a list of relays that users can choose from:

https://nostr.watch/relays.json

We should also pick a few default ones.

The relay management should support url, write and read properties. Relays should also be organizable in order (priority).

[sondreb]

Relays should be managed pr. account, allowing users to have different relays for different accounts.

This means there has to be some logic that queries permissions for public key for the website in question to pick which list of relays to return. And if user chooses "Only once" for pubkey permission, we will show account selection on the relay-allow popup.