Starting to implement OPAQUE in Swift

Not sure if this will be interesting to anyone, but I've started a toy implementation of the OPAQUE protocol in Swift. I had a hard time finding information and resources about this protocol, and I link to a few throughout the README for those of you that are interested in such things. It is currently very early stages, but I have a working(?) implementation of an OPRF, which is more than I found available elsewhere, so I figured I'd clean it up for anyone else wandering down the same roads I did.