This NIP is not yet in main. Here is an overview of PRs referencing this NIP. 
flesh out NIP-77 (negentropy syncing) MERGED @hoytech
NIP-77: Negentropy syncing OPEN @fiatjaf
Add NIP-77 for expressing trust OPEN @lez
NIP-77 - Trust Clock CLOSED @arthurfranca
NIP-0077: nostr-share deeplink/uri scheme for sharing images and text OPEN @mandelmonkey