post menu and file attachments (#2414)

* post menu and file attachments

* Fix post list selector test

* Use new Gesture handler to avoid gesture conflicts in post menu and reaction list

* Allow reaction list to scroll the header on Android

* Feedback review

* Add some comments

* Fix eslint

android/app/src/main/java/com/mattermost/rnbeta/MainApplication.java

@@ -24,6 +24,7 @@ import com.gantix.JailMonkey.JailMonkeyPackage;
 import io.tradle.react.LocalAuthPackage;
 import com.github.godness84.RNRecyclerViewList.RNRecyclerviewListPackage;
 import com.reactnativecommunity.webview.RNCWebViewPackage;
+import com.swmansion.gesturehandler.react.RNGestureHandlerPackage;
 
 import com.facebook.react.ReactPackage;
 import com.facebook.soloader.SoLoader;
@@ -84,7 +85,8 @@ public class MainApplication extends NavigationApplication implements INotificat
             new KeychainPackage(),
             new InitializationPackage(this),
             new RNRecyclerviewListPackage(),
-            new RNCWebViewPackage()
+            new RNCWebViewPackage(),
+            new RNGestureHandlerPackage()
     );
   }