25519 keys not supported

[keks]

25519 keys are not supported because golang.org/x/crypto/openpgp doesn't support them. Maybe we can fix that upstream? I'll see what I can do.

[keks]

Looks like 25519 is not in the RFC yet? I guess contributing upstream will be tricky if its not in the standards...but yeah its not lvl0 anyway.

[keks]

@dkg @hpk42 What is your take on this?

[keks]

upstream: golang/go#18576

[hpk42]

@dkg is more qualified to answer this and i think he did already.