Added documentation for the game controller axis values
diff --git a/include/SDL_gamecontroller.h b/include/SDL_gamecontroller.h
index 36af08d..1997471 100644
--- a/include/SDL_gamecontroller.h
+++ b/include/SDL_gamecontroller.h
@@ -247,6 +247,12 @@ extern DECLSPEC void SDLCALL SDL_GameControllerUpdate(void);
/**
* The list of axes available from a controller
+ *
+ * Thumbstick axis values range from SDL_JOYSTICK_AXIS_MIN to SDL_JOYSTICK_AXIS_MAX,
+ * and are centered within ~8000 of zero, though advanced UI will allow users to set
+ * or autodetect the dead zone, which varies between controllers.
+ *
+ * Trigger axis values range from 0 to SDL_JOYSTICK_AXIS_MAX.
*/
typedef enum
{