Petnames - publishing contact lists

See: https://files.spritely.institute/papers/petnames.html

While we use public keys to identify peers, we'll want to have human-friendly local names for these so the user can manage them easily. The petnames system suggests optionally sharing these human-friendly labels as a contact list searchable by your own contacts. This seems a good discovery mechanism without having to necessarily contact each person you want to collaborate with on other channels first.