The path to the target node, relative to the
VisibleOnScreenEnabler2D. The target node is cached; it's only assigned when setting this property (if the
VisibleOnScreenEnabler2D is inside the scene tree) and every time the
VisibleOnScreenEnabler2D enters the scene tree. If the path is empty, no node will be affected. If the path is invalid, an error is also generated.