Basic weather app demonstrating SwiftUI implementation with MVVM.

• Using WeatherStack API to fetch current/forecast weather (https://weatherstack.com)
• Added some unit tests to showcase the flow.

Improvements:

• Environment could be used instead of injecting client.
• Environment variable can be managed by build configurations and targets.
• Views can depend on a viewmodel state variable rather than multiple @Published.
• We could use latest Swift concurrency (@Observable) if we have to support only latest iOS.
• Improve code coverage by testing all the features.