Note which Windows SDK version is required for Windows Gaming Input support

include/SDL_config_windows.h

@@ -198,7 +198,7 @@ typedef unsigned int uintptr_t;
 #define SDL_JOYSTICK_HIDAPI 1
 #define SDL_JOYSTICK_RAWINPUT   1
 #define SDL_JOYSTICK_VIRTUAL    1
-/*#define SDL_JOYSTICK_WGI    1*/
+/*#define SDL_JOYSTICK_WGI    1*/   /* This requires Windows SDK 10.0.16299.0 */
 #define SDL_JOYSTICK_XINPUT 1
 #define SDL_HAPTIC_DINPUT   1
 #define SDL_HAPTIC_XINPUT   1