Prevent modal dismissal with swipe gestures

Summary:
iOS 13 introduced interactive dismissal for modals https://medium.com/hacknicity/view-controller-presentation-changes-in-ios-13-ac8c901ebc4e.

This breaks react modals. We're disabling this feature for react modals

Changelog: [iOS][Fixed]  Prevent interactive dismissal for non-fullscreen modals

Reviewed By: shergin

Differential Revision: D19836548

fbshipit-source-id: 2b8c80b863569af48ff1c2cf74658393b1b583fd

React/Views/RCTModalHostViewController.m

@@ -24,7 +24,11 @@
   if (!(self = [super init])) {
     return nil;
   }
-
+    
+  if (@available(iOS 13.0, *)) {
+    self.modalInPresentation = YES;
+  }
+    
 #if !TARGET_OS_TV
   _preferredStatusBarStyle = [RCTSharedApplication() statusBarStyle];
   _preferredStatusBarHidden = [RCTSharedApplication() isStatusBarHidden];