- Widget's with styles must also include a ComputedStyles component and set it to equal to your styles object.

Also added trait bounds to Widget since its trait object has been replaced by
BaseWidget.

Added the CursorEvent struct to the cursor-related enum variants on
EventType

Also changed how PartialEq and Hash work for EventType. They no longer
consider the inner variant data

Also added to KayakContext (as interface for Bevy) and to
EventDispatcher (where it's managed)

These allow us to pass along metadata with a keyboard event
(specifically here, which modifier keys are active)