Draft: Add macOS support

This MR contains Bindings.xcframework build manually from client repo, using the following script:

go mod tidy
rm -rf vendor/
go build ./...
go get golang.org/x/mobile/bind
go install golang.org/x/mobile/cmd/gomobile@latest
gomobile init
gomobile bind -target ios,iossimulator,macos gitlab.com/elixxir/client/bindings

go version go1.17.13 darwin/arm64

README.md

 # Elixxir dApps Swift SDK
 
 ![Swift 5.6](https://img.shields.io/badge/swift-5.6-orange.svg)
-![platform iOS](https://img.shields.io/badge/platform-iOS-blue.svg)
+![platform iOS, macOS](https://img.shields.io/badge/platform-iOS,_macOS-blue.svg)
 
 ## 📖 Documentation