code: function bounds(boxes) {
  	var width = 0
  	var height = 0
  	for (var i = 0; i < boxes.length; i++) {
  		var box = boxes[i]
  		var right = box.position[0] + box.size[0]
  		var bottom = box.position[1] + box.size[1]
  		if (right > width) {
  			width = right
  		}
  		if (bottom > height) {
  			height = bottom
  		}
  	}
  	return [ width, height ]
  }
docs: finds the smallest `[ width, height ]` vector that contains all `boxes`