Add singlerider PGP key to .sops.yaml

[singlerider]

I'm adding my PGP key (used to sign commit(s)):

3D7C8D39E8C4DF771583D3F0A8A091FD346001CA

This is for the purpose of ops permissions to deploy a Mastodon instance.

[drGrove]

Ops permissions and working on adding services aren't mutually exclusive. You you provide us with a means to generate said password and where it needs to be set we can do that