fix new NativeEventEmitter() was called with a non-null argument without the required listener warning (microsoft#2324)

Co-authored-by: Hernan Paris <hernanparis@Hernans-MBP.fibertel.com.ar>

Author: herparis

android/app/src/main/java/com/microsoft/codepush/react/CodePushNativeModule.java

@@ -693,4 +693,14 @@ public void clearUpdates() {
         CodePushUtils.log("Clearing updates.");
         mCodePush.clearUpdates();
     }
+
+    @ReactMethod
+    public void addListener(String eventName) {
+        // Set up any upstream listeners or background tasks as necessary
+    }
+
+    @ReactMethod
+    public void removeListeners(Integer count) {
+        // Remove upstream listeners, stop unnecessary background tasks
+    }
 }