Adds an event handler that runs when the element is double-clicked.
An element receives a dblClick event when a user double-clicks on the element
and releases.
When a user double-clicks an element, two click events are fired
before a doubleClick event is also fired.
You can also define an event handler using the Properties and Events panel.
handler(event: MouseEvent): void The name of the function or the function expression to run when the element is clicked.