Add support for Sodium().pwhash.scryptsalsa208sha256

[blaineam]

I need this algorithm from libsodium to be available via swift is there any way you can add support for this? I see you are importing it from Clibsodium but don't have any implementation of it in swift yet.

Sodium().pwhash.scryptsalsa208sha256

Also, do I need to call something like this after calling Sodium().secretBox.seal...

Sodium().utils.increment(&nonce) because this does not appear to be implemented so Im guessing its not needed.