Move RCTLinkingManager to the main thread

Reviewed By: shergin

Differential Revision: D4709352

fbshipit-source-id: 3fc86504b12fe64dd94dd7330073d1a4a4f272e2

Libraries/LinkingIOS/RCTLinkingManager.m

@@ -19,6 +19,11 @@ NSString *const RCTOpenURLNotification = @"RCTOpenURLNotification";
 
 RCT_EXPORT_MODULE()
 
+- (dispatch_queue_t)methodQueue
+{
+  return dispatch_get_main_queue();
+}
+
 - (void)startObserving
 {
   [[NSNotificationCenter defaultCenter] addObserver:self