Feature: nos2x/alby/nip07 support

[Giszmo]

Many more advanced users dread giving many apps their private keys, so they use nos2x or alby to sign events or decrypt messages.

https://github.com/nostr-protocol/nips/blob/master/07.md

• [ ] Check if Alby supports DMs and works for Chrome and FF
• [ ] If not, check the difference between nos2x for FF and for Chrome
• [ ] Implement window.nostr.signEvent() if pubkey is window.nostr.getPublicKey()

Implementation of support for account addition from window.nostr.getPublicKey() "Your nostr extension has an account you haven't added yet. Do you want to use with Nostroid?". Is low priority.

[Giszmo]

An XSS vulnerability in Anigma that could have resulted in the leak of most users' keys just bumped this issue from MVP+1 to MVP. It should be easy to implement. Beware the nos2x working differently on FF and Chrome. Alby might still not support DMs ...