[cm/pub/] with Ed25519.

Same calculation and serialisation rules must be used as with
[cm/signed/ed25519-blake2b].

Public key's fingerprint should be calculated using BLAKE2b hash
with 256 bit output length specified.
=> RFC 7693, BLAKE2b

Its /data/pub contents:
    pub-ed25519-blake2b {
        {field . {map}}
        {field a {str} =ed25519-blake2b}
        {field v {bin} len=32}
    }