dispose method

Implementation

@override
void dispose() {
  // remove event listeners
  EventManager.of(widget.model)
      ?.removeEventListener(EventTypes.scroll, onScroll);
  EventManager.of(widget.model)?.removeEventListener(EventTypes.sort, onSort);
  EventManager.of(widget.model)
      ?.removeEventListener(EventTypes.scrollto, onScrollTo);

  controller.dispose();
  super.dispose();
}