Expand
ui:expand
Indicates that a component is expanded.
This event is fired when you expand the ui:menuList component. To set a handler for the ui:expand event, use the menuExpand attribute on ui:menuList.
The following example adds or remove a CSS class to the ui:menuList component when it's collapsed or expanded.
Here's the client-side controller that handles the adding and removing of the CSS classes.
If you're using this event with a component other than ui:menuList, register the event first.
