states_rebuilder implementation

[GIfatahTH]

First of all, I would like to thank you for your efforts and contributions in making the flutter community better. I also appreciate being open to other state management solutions. This is my contribution to your project. It consists of a states_rebuilder implementation. It should be noted that:

• I did not touch the core part. I took it as it is and just consume it.
• By default, states_rebuilder tracks the state status and exposes six flags:
• isIdle: after the state is first created and before any operation (virgin status).
• isWaiting: When the state is waiting for an async task (Future or Stream).
• hasError: If the state caught an exception.
• hasData: when the state is mutated successfully with valid data
• isDone: when the state's stream is done.
• isActive: changed manually to mark whether the state is active or not.
• If the sole purpose of using Freezed is to track one of the six state status, then it is no longer necessary to use it.
• I do not use favouriteMovies that use RxDart. Instead, I combined two injected states.
• All the functionalities of the app are tested.

[bizz84]

@GIfatahTH thank you very much for this PR and apologies for the delay. Merged now.

[bizz84]

@GIfatahTH When you get a chance could you make a new PR and migrate this implementation to null safety?