An example of the BLoC pattern.
This is similar to the Flutter-Redux-Pattern in functionality but is
different in form. The exampleBloc contains the business logic and the
exampleProvider extends from InheritedWidget and is used by wrapping
the main screen where the BLoC is created. Access to the block can be
seen in the exampleScreen widget where it is picked up through the
context.
Note that the BLoC contains no Flutter imports.