Is your feature request related to a problem? Please describe.
I often find myself in the situation where I need both bloc builders and bloc listeners in the same widget tree, e.g. for showing a loading indicator (builder) and displaying a snackbar on success (listener).

Describe the solution you'd like
A BlocBuilderListener Widget that accepts both a builder function and a listener would greatly reduce the clutter in my code and also reduce the overhead of having two stateful widgets that basically do the same. Alternatively, you could add a listener parameter to the existing BlocBuilder widget.