Write an app that simulates a traffic light. It displays a label and a button; the label represents the current colour of a traffic light and can be red, yellow, or green. When the user clicks on the button, the label cycles to the next colour and simulates running the traffic light. You should look at the documentation of the View class to figure out how to change the colour of a View by code. The two components should be centred vertically, the button below the label.