Creates a Graphics Game Object that the world will use to render the debug display to.
This is called automatically when the World is instantiated if the
debug config property
was set to
true. However, you can call it at any point should you need to display the
debug Graphic from a fixed point.
You can control which objects are drawn to the Graphics object, and the colors they use, by setting the debug properties in the physics config.
You should not typically use this in a production game. Use it to aid during debugging.
The Graphics object that was created for use by the World.