Support APIs for the Swift language

[iyangsj]

Reference： https://mozilla.github.io/uniffi-rs/

[delneg]

Hi! I've taken a look and noticed, that there are already headers in "include" directory which can be used from C easily.

In case of Swift, it may be easier to create an .xcframework which will contain: the binary itself, the .h file, and the Swift bindings which can be hand-written to have "Swifter" user-facing API. Then, it can be consumed by users via Cocoapods or SwiftPM and provide smooth UX.

(That's an alternative to UniFFI approach, which has it's pros and cons)