Add ed25519 fingerprints

RSA fingerprints are vestigial, and kept around purely to ease transition to ed25519 keys. Anything currently relying on them should be making that transition now, so they may be dropped entirely at some point in the future. As such, Onionoo should give them equal treatment.

I have been asked to open this issue on behalf of nusenu, who maintains the ContactInfo Information Sharing Specification.