This adds server-side support for the newly introduced OpenSSH keytypes sk-ecdsa-sha2-nistp256@openssh.com and sk-ed25519@openssh.com (including their corresponding certificates), which are backed by U2F/FIDO2 tokens. Change-Id: I53d5ed3d0457ae4758ee986055e187ee5787a2d1 Reviewed-on: https://go-review.googlesource.com/c/crypto/+/208017 Reviewed-by: Han-Wen Nienhuys <hanwen@google.com> Run-TryBot: Han-Wen Nienhuys <hanwen@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org>