EXAMPLES: replaced cube_dynamic with cube_dynamic2, added car controls

[looeee]

As discussed in #13223:

• renamed webgl_materials_cube_dynamic2 to webgl_materials_cube_dynamic
• created new misc_controls_car example to showcase the Car.js file

I've updated Car.js as follow:

• it now handles controls and setting up event listeners internally
• no longer handles loading and creation of meshes, so it can use a suitable model loaded by any loader
• (very roughly!) uses real world units
• calculates all car dimensions automatically
• cars now have a brake! (use space)

It takes a model that must have 4 wheels, which can be Groups, Object3Ds or Meshes and must be named wheelFrontLeft, wheelFrontRight, wheelRearLeft and wheelRearRight.

Live version of the new example here.

[looeee]

Updated:

• improved the model a bit (now just over 100k polys and less gaps)
• added optional steering wheel rotation
• added "zoom in" effect when the car has first loaded

Updated link

[mrdoob]

I think I would use a normal GridHelper instead. The radial one is confusing in this example.

[looeee]

OK, done!

[looeee]

Closed in favour of #14843