Implement authentification from Scuttlebutt .ssb file

Scuttlebutt store the secret key-pair of a user in the $HOME/.ssb folder.

Add support for authentication by loading the ssb file.

Scuttlebutt key-pair is of the same ed25519 protocol than Duniter.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information