iOS 13 and CryptoKit

[laszlo-major]

Apple seems to have broken Security.framework in iOS 13+ simulators, while at the same releasing CryptoKit as a standard way of doing crypto operations, limited to iOS 13 and higher.

It would be really nice if the library could transparently implement operations with Cryptokit where available while keeping the same pleasant API.

[wuf810]

This is the same issue:

#46