Make the list items accessible (#1439)

We noticed that one of the views for selecting images was not accessible and would like to make it accessible. This was based on user feedback.

ios/QBImagePicker/QBImagePicker/QBAssetsViewController.m

@@ -472,6 +472,7 @@ - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cell
     QBAssetCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"AssetCell" forIndexPath:indexPath];
     cell.tag = indexPath.item;
     cell.showsOverlayViewWhenSelected = self.imagePickerController.allowsMultipleSelection;
+    cell.isAccessibilityElement = true;
 
     // Image
     PHAsset *asset = self.fetchResult[indexPath.item];