chore: Update BG recording docs.

Author: llfbandit

doc/bg_recording.md

@@ -17,10 +17,18 @@ Add the following the manifest in `android/app/src/main/AndroidManifest.xml`:
         android:foregroundServiceType="microphone"
         android:exported="false" />
 </application>
+```
 
-A notification is added to conform to Android requirements.
+When starting recording, you need to enable the service explicitly by setting the following in the given config:
+```dart
+RecordConfig(
+  ...,
+  androidConfig: AndroidRecordConfig(service: AndroidService(title: 'Title', content: 'Content...'))
+);
 ```
 
+A notification is added to conform to Android requirements if service is started.
+
 ## iOS
 
 Add the following in `ios/Runner/info.plist`: