A modification that applies the transforms of [PhysicalBone2D] nodes to [Bone2D] nodes. This modification takes the transforms of [PhysicalBone2D] nodes and applies them to [Bone2D] nodes. This allows the [Bone2D] nodes to react to physics thanks to the linked [PhysicalBone2D] nodes. Empties the list of [PhysicalBone2D] nodes and populates it will all [PhysicalBone2D] nodes that are children of the [Skeleton2D]. The amount of [PhysicalBone2D] nodes linked in this modification.