Add MessengerRegisterForNotifications function

See merge request elixxir/elixxir-dapps-sdk-swift!70

Encode/decode empty facts array to/from "null"

See merge request elixxir/elixxir-dapps-sdk-swift!69

Update Bindings.xcframework

See merge request elixxir/elixxir-dapps-sdk-swift!66

elixxir/client@6c1ccd50
go version go1.17.13 darwin/arm64
Xcode 13.4.1 Build version 13F100
gomobile bind target: ios,iossimulator,macos

Messenger example - user search

See merge request elixxir/elixxir-dapps-sdk-swift!65

XXMessengerClient - Search Users

See merge request elixxir/elixxir-dapps-sdk-swift!64