Experimental tessellation

Adding geometry/vertex tessellation

• This feature is enabled with medium terrain quality setting.
• It will interpolate geometry to look smother, but it will strain your
  GPU quite a bit, e.g. 15% loss in fps is not out of the ordinary.
• This mod is meant for people who either like visual fidelty vs fps,
  or simply have the money for the best GPU available, even though
  it may still bring a RTX 4090 to its limit on 4k and ultra setting :)