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.c

@@ -42,7 +42,7 @@
 //...
 
 //----------------------------------------------------------------------------------
-// Module Functions Definition
+// Module Functions Declarations
 //----------------------------------------------------------------------------------
 
 // Lights functions