Add RELATIVE_ORIENTATION sensor implementation on macOS to //device/generic_sensor

device/generic_sensor/README.md

Index: device/generic_sensor/README.md
diff --git a/device/generic_sensor/README.md b/device/generic_sensor/README.md
index e1842f971abc9bec5662e237e2722693af4ff3cd..ab0e5375017853b178c3ceea5b3bf8c6047be699 100644
--- a/device/generic_sensor/README.md
+++ b/device/generic_sensor/README.md
@@ -24,7 +24,7 @@ platform.
 | MAGNETOMETER         | TYPE_MAGNETIC_FIELD       | in_magn        |                    | SENSOR_TYPE_COMPASS_3D                    |
 | PRESSURE             |                           |                |                    |                                           |
 | ABSOLUTE_ORIENTATION | TYPE_ROTATION_VECTOR      |                |                    | SENSOR_TYPE_AGGREGATED_DEVICE_ORIENTATION |
-| RELATIVE_ORIENTATION | TYPE_GAME_ROTATION_VECTOR |                |                    |                                           |
+| RELATIVE_ORIENTATION | TYPE_GAME_ROTATION_VECTOR |                | ACCELEROMETER      |                                           |
 
 ### Android
 
@@ -45,7 +45,8 @@ searches for to provide data for a SensorType.
 On this platform there is limited support for sensors. The AMBIENT_LIGHT sensor
 type is provided by interpreting the value that can be read from the LMU. The
 ACCELEROMETER sensor type is provided by interpreting the value that can be read
-from the SMCMotionSensor.
+from the SMCMotionSensor. The RELATIVE_ORIENTATION sensor type is provided by
+interpreting the value that can be read from the ACCELEROMETER.
 
 ### Windows