fix: improve documentation

Author: holzgeist

README.md

@@ -34,6 +34,8 @@ Regarding permissions, you may need the following settings in your `AndroidManif
     <uses-permission android:name="android.hardware.sensor.proximity"/>
     <uses-permission android:name="android.permission.BODY_SENSORS_BACKGROUND"/>
     <uses-permission android:name="android.permission.ACTIVITY_RECOGNITION"/>
-    <uses-permission android:name="android.permission.ACTIVITY_RECOGNITION"/>
+    <uses-permission android:name="android.permission.WAKE_LOCK"/>
+
+NB: the WAKE_LOCK permission is only needed if you run `setProximityScreenOff(true)` before listening to events
 
 **Some recent devices use virtual proximity sensors. There are no physical sensors. I found it hard to trust the sensor information in this case.**