Pre-Shared Key Support

[quininer]

The PSK should be part of the protocol?

[quininer]

We should use a mixed mode, like noise protocol.

// ooake(ristrettodh)@psk@kyber-aes128colm0

let mut state = State::new();
state.mix(ooake::<ristrettodh>());
state.mix(psk);
state.mix(kyber());
let key = state.key();

aes128colm0(key);