renamed self to data for transformable interface

src/transformable.h

@@ -12,7 +12,7 @@ typedef struct {
 } ITransformable;
 
 typedef struct {
-    void* self;
+    void* data;
     ITransformable const* tc;
 } Transformable;
 
@@ -27,7 +27,7 @@ static inline Transformable T##_as_Transformable(T* x) {\
         .get_scale =        (Vector*(*const)(void*))    get_scale_f,\
         .get_rotation =     (float*(*const)(void*))     get_rotation_f\
     };\
-    return (Transformable){.tc = &tc, .self = x };\
+    return (Transformable){.tc = &tc, .data = x };\
 }
 
 #endif // !_fencer_transformable_h