Fired when composition is updated inside one of the editables.
Introduced by CompositionObserver.
CompositionObserver
Note that because CompositionObserver is attached by the EditingView this event is available by default.
EditingView
args : tuple
module:engine/view/observer/compositionobserver~ViewDocumentCompositionUpdateEvent#args
name : 'compositionupdate'
module:engine/view/observer/compositionobserver~ViewDocumentCompositionUpdateEvent#name