Contains a [Curve2D] path for [PathFollow2D] nodes to follow. Can have [PathFollow2D] child-nodes moving along the [Curve2D]. See [PathFollow2D] for more information on this usage. Note that the path is considered as relative to the moved nodes (children of [PathFollow2D]) - usually the curve should start with a zero vector (0, 0). A [Curve2D] describing the path.