Allow coroutines on add_listener.

The current code that process a notification uses the method call_soon which expects a callable, why not to use create_task (or ensure_future for compatibility reasons) after checking if the callback is a coroutine?

There are different ways to do this, either just checking if the callback is a coroutine as described in here for example. Another way is just to add an extra argument or a different method to register coroutines.

Would it make sense to add a context? I am currently passing extra arguments to the callback via functools.partial.

Let me know if something like this would be accepted I can create a PR with the implementation.

Comienza en el punto de entrada add_listener y en el procesamiento de notificaciones que actualmente llama a call_soon. Compara create_task y ensure_future para callbacks de coroutine, incluido el uso existente de functools.partial para argumentos adicionales. Done debe incluir una API de callbacks acordada y un comportamiento de compatibilidad, con pruebas que cubran listeners normales y de coroutine.