[feat] Add Relay Groups

[leesalminen]

This PR allows users to create groups of relays which can then be selected when writing notes and viewing feed.

Still a WIP.

[monlovesmango]

first off, I love this. thank you. please continue.

a few bits of feedback I have. first, I am hoping to have completely customized feeds in the future. meaning that you can choose the relay group when you are creating your feed in settings and shouldn't need the option in the feed. gonna be upgrading to latest nostr-tools version and re-writing the relay query pool to handle this.

second, i think i would prefer the relay config to be a small compact drop down from the top, but this is easy for me to rearrange later if you don't want to deal with this. I want the menu you put the relay config in to be for editing content only. editing metadata or relays for the event I want to be more general. I also want a dropdown for choosing language at some point, incase that gives more context on my delineation between editing content and editing event behavior.

last thing, I would really like a draft nip at the very least that we can implement as poc. I think users would really like to be able to group their relays and want them to be able to take these groupings elsewhere.

just wanted to give some of my thoughts/plans. let me know if you disagree anywhere or have differing viewpoint.