Added raylib-lua-ffi

CONTRIBUTING.md

@@ -61,6 +61,7 @@ Some people ported raylib to other languages in form of bindings or wrappers to
 
  - [raylib](https://github.com/raysan5/raylib) : raylib **C/C++** version (default)
  - [raylib-lua](https://github.com/raysan5/raylib-lua) : raylib **Lua** binding
+ - [raylib-lua-ffi](https://github.com/raysan5/raylib/issues/693) : raylib **Lua** ffi binding
  - [raylib-go](https://github.com/gen2brain/raylib-go) : raylib **Go** binding
  - [raylib-Nim](https://gitlab.com/define-private-public/raylib-Nim) : raylib **Nim** binding
  - [cray](https://gitlab.com/Zatherz/cray) - raylib **Crystal** binding