Add SDL_SENSOR_COUNT to SDL_SensorType

include/SDL3/SDL_sensor.h

@@ -138,7 +138,8 @@ typedef enum SDL_SensorType
     SDL_SENSOR_ACCEL_L,         /**< Accelerometer for left Joy-Con controller and Wii nunchuk */
     SDL_SENSOR_GYRO_L,          /**< Gyroscope for left Joy-Con controller */
     SDL_SENSOR_ACCEL_R,         /**< Accelerometer for right Joy-Con controller */
-    SDL_SENSOR_GYRO_R           /**< Gyroscope for right Joy-Con controller */
+    SDL_SENSOR_GYRO_R,          /**< Gyroscope for right Joy-Con controller */
+    SDL_SENSOR_COUNT
 } SDL_SensorType;