Added physics engine-module and example

- Added new physics engine-module with four new data types: Physics,
Transform, Rigidbody and Collider. This library contains functions to
apply physics calculations to a position vector calculating collisions
automatically.

- Fixed some writing mistakes of lighting module.

src/lighting.h

@@ -61,7 +61,7 @@ typedef struct Material {
 } Material;
 
 //----------------------------------------------------------------------------------
-// Module Functions Declaration 
+// Module Functions Definitions
 // NOTE: light and material structs uses float pointers instead of vectors to be compatible with SetShaderValue()
 //----------------------------------------------------------------------------------
 // Lights functions