* Made the whole block a separated scene to demonstrate it can work across multiple instances.
* Dropped the Area.input_event and did everything manually with raycasting.
* Made quad_mesh_size automatically pick the quad size, avoiding the extra setup.
* Changed from PlaneMesh to QuadMesh. Now everyting can start with 0 rotation.
* The function will keep handling input when the mouse is outside of the area to avoid orphan clicks, but stop when the click is released.
* Changed some variable and function names to make sense with the code changes.
* Added an extra function to deal with billboard mode. But is not perfect, specially with scaling and Y-billboard + camera tilting.
