add isShadow flag if a node is under shadow root

src/snapshot.ts

@@ -8,7 +8,7 @@ import {
   MaskInputOptions,
   SlimDOMOptions,
 } from './types';
-import { isElement } from './utils';
+import { isElement, isShadowRoot } from './utils';
 
 let _id = 1;
 const tagNameRegex = RegExp('[^a-z0-9-_]');
@@ -657,6 +657,10 @@ export function serializeNodeWithId(
     }
   }
 
+  if (n.parentNode && isShadowRoot(n.parentNode)) {
+    serializedNode.isShadow = true;
+  }
+
   if (
     serializedNode.type === NodeType.Element &&
     serializedNode.tagName === 'iframe'