4 swivel front wheels

The script adds two more swivel wheels to 8x8, 8x6 and 8x4 vehicles (after manual adaptation of the model).
Extra wheels don't get pierced, and have no collision, but they cushion (repeate the movements of the front wheels).

Instructions for adapting the model to the script:

1. Import the desired model into a 3D editor (ZModeler 2.2);
2. Using a 3D editor (ZModeler 2.2), create a dummy in the imported model; additional wheels: wheel_rf2_dummy (right), wheel_lf2_dummy (left);
3. Place the wheel geometries into dummy wheel_rf2_dummy (right) and wheel_lf2_dummy (left);
4. Change the thickness of the wheels so that all the wheels in the game are the same width;
5. Export the model to the game.

Many thanks to modmaker ! for the Wheel_4x.cs script! Artem.1.9.9.6!