||Creates a new watcher for the element represented by self (the object the method is being invoked for).
- a function to be called when a watched event occurs. The argument will be passed the following arguments:
- element: The element the event occurred on. Note this is not always the element being watched.
- event: The name of the event that occurred.
- watcher: The watcher object being created.
- userData: The userData you included, if any.
- an optional userData object which will be included as the final argument to the callback function when it is called.
- An `hs.uielement.watcher` object, or `nil` if an error occurred