extensions/either_extentions library

1. i_tdd package
2. documentation
3. extensions/either_extentions.dart

i_tdd package

1. Libraries
2. domain/models/params
3. domain/usecases/i_usecase
4. extensions/cubit_error_handling_extension
5. extensions/either_extentions
6. extensions/future_data_loading_extensions
7. extensions/future_stream_data_loading_extensions
8. extensions/stream_data_handling_extensions
9. extensions/stream_data_loading_extensions
10. i_tdd
11. type_def/either_type_def