Add my new Ed25519 OpenPGP key

I have created a new OpenPGP key and will be transitioning away from my
old key. I have no reason to believe the old key has been compromised.
It was old and due for replacement.

My old key will continue to be valid for some time, but I prefer all
future correspondence to be encrypted with the new key. I will be
making all signatures going forward with the new key.

In due course I will remove my old 2048 bit RSA key from the repo.