SDL_main.h: added field to SDL_GDKSuspendComplete documentation.

include/SDL_main.h

@@ -266,6 +266,7 @@ extern DECLSPEC int SDLCALL SDL_GDKRunApp(SDL_main_func mainFunction, void *rese
 /**
  * Callback from the application to let the suspend continue.
  *
+ * \since This function is available since SDL 2.28.0.
  */
 extern DECLSPEC void SDLCALL SDL_GDKSuspendComplete(void);