Add UI for DM's somewhere in the app which explains how to use a different app for DM's

[rabble]

Right now we don't explain to users that DM's are possible. I think we should put somewhere in the UI an option for DM's which explains that while Nos doesn't do DMs you can send and receive them with your nostr identity and that you could use your nsec account in a list of other nostr apps to send and receive DMS.