core/Error/failures library

1. fast_http package
2. documentation
3. core/Error/failures.dart

fast_http package

1. Libraries
2. core/API/generic_request
3. core/API/header_manager
4. core/API/request_method
5. core/Error/error_message_model
6. core/Error/exceptions
7. core/Error/failures
8. fast_http