Change the multi-state box's current state to a specific state.
The changeState() function returns a Promise that is resolved when
the multi-state box finishes moving from the current state to the state
referred to by stateReference. stateReference can be a state object or
a state id.
You can retrieve State objects to pass to the
stateReference parameter from your multi-state box using the
currentState or states properties.
Note:
If you call changeState() on a child multi-state box, it doesn't run until the parent box moves to the state where the child box is displayed.