Make ImagePickerIOS.openCameraDialog work with video (fixes #17989) (#19170)

Summary:
Fixes #17989

Previously, `ImagePickerIOS.openCameraDialog` would not render a `Video` option when the camera screen opened. If you passed `ImagePickerIOS.openCameraDialog({ videoMode: true }, ...)` the app would crash with an error complaining about the proper mediaType(s) not being set (see issue: #17989  for full details).

This is a 2 line change that sets the mediaTypes properly, so now users can capture videos in addition to photos.
Pull Request resolved: #19170

Differential Revision: D14068078

Pulled By: hramos

fbshipit-source-id: d04a3d267ca83ea58e88c880a85ac34ddd4744c8

Author: jcarver989

Libraries/CameraRoll/RCTImagePickerManager.m

@@ -85,6 +85,8 @@ - (dispatch_queue_t)methodQueue
   RCTImagePickerController *imagePicker = [RCTImagePickerController new];
   imagePicker.delegate = self;
   imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;
+  NSArray<NSString *> *availableMediaTypes = [UIImagePickerController availableMediaTypesForSourceType:UIImagePickerControllerSourceTypeCamera];
+  imagePicker.mediaTypes = availableMediaTypes;
   imagePicker.unmirrorFrontFacingCamera = [RCTConvert BOOL:config[@"unmirrorFrontFacingCamera"]];
 
   if ([RCTConvert BOOL:config[@"videoMode"]]) {