Make POC for iOS

[fedyiv]

Summary:
The goal is to prove that library can be run on iOS and perform connection initiation with remote agent

TO DO:

1. Take **develop branch of current repository.
2. Run .NET Aries agent with websockets locally
3. Ensure you can run current SsiAgentApiImplTest on JVM and establish connection with remote agent
4. Review https://kotlinlang.org/docs/multiplatform.html to get a concept of kotlin multiplatform
5. Implement all missing parts in iosMain part of the repo.
6. Understand how libindy is packed into current DXC SSI library (in master branch) and pack it similarly in iOS part.
7. Ensure test SsiAgentApiImplTest passes on iOS
8. In Readme document following:
   • prerequisites
   • how to build
   • how to run test
   • how client can use this library

Definition of Done:

1. SsiAgentApiImplTest is passing on iOS

Useful info:

1. For adding iOS dependencies install and configure cocoapods.
   See https://kotlinlang.org/docs/mobile/add-dependencies.html#ios-dependencies
   and https://kotlinlang.org/docs/native-cocoapods.html#install-the-cocoapods-dependency-manager-and-plugin

2. See details on how to implement WebSockets on iOS:
   https://kotlinlang.org/docs/mobile/connect-to-platform-specific-apis.html#example-send-and-receive-messages-from-a-websocket