fix(ios): allow overlap

Author: farfromrefug

src/collectionview/index.ios.ts

@@ -908,6 +908,10 @@ export class CollectionView extends CollectionViewBase {
         if (!cell) {
             cell = CollectionViewCell.new() as CollectionViewCell;
         }
+        // should we force clipsToBounds? not doing so allows more complex layouts like overlapping
+        // cell.clipsToBounds = true;
+        // we set zPosition to allow overlap. Should we make it an option?
+        cell.layer.zPosition = indexPath.row;
         const firstRender = !cell.view;
         if (Trace.isEnabled()) {
             CLog(CLogTypes.log, 'collectionViewCellForItemAtIndexPath', indexPath.row, templateType, !!cell.view, cell);