Use `bevy_eventlistener` as the event dispatcher

[musjj]

This will allow you to ergonomically deal with events on specific entities. For example:

commands.spawn((
    ButtonBundle::default(),
    Focusable::default(),
    On::<Focused>::run(focused),
    On::<Active>::run(active),
    On::<Prioritized>::run(prioritized),
    On::<Inert>::run(inert),
    On::<Blocked>::run(blocked),
));