Add encryption support for node-red/join communication

Withouth encryption support in node-red-contrib-join-joaoapps, node-red cannot be part of a join "network" which is using encryption.

So far I can't use node-red as a device, since I have setup encryption between all my devices. Just join for node-red seems not (yet?) to have this feature.

Could we have encryption for node-red-contrib-join-joaoapps?