Update README.md, fix flutter-webrtc#211

cloudwebrtc · web-flow · commit c6423b2afcb9 · 2020-09-27T07:34:33.000+08:00
Added description of Bluetooth device permissions for Android.
diff --git a/README.md b/README.md
@@ -42,6 +42,12 @@ Ensure the following permission is present in your Android Manifest file, locate
 <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
 ```
 
+If you need to use a Bluetooth device, please add:
+```xml
+<uses-permission android:name="android.permission.BLUETOOTH" />
+<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
+```
+
 The Flutter project template adds it, so it may already be there.
 
 Also you will need to set your build settings to Java 8, because official WebRTC jar now uses static methods in `EglBase` interface. Just add this to your app level `build.gradle`:
