duplicateByDOMNode method
Duplicates domNode in the parent children list. Also performs on mapped element.
Implementation
DOMNodeMapping<T>? duplicateByDOMNode(DOMNode? domNode) {
  if (domNode == null || !domNode.hasParent) return null;
  var nodeRuntime = domNode.runtime;
  var domCopy = domNode.duplicate();
  var copy = nodeRuntime.duplicate();
  if (domCopy == null && copy == null) return null;
  if (domCopy != null && copy != null) {
    mapTree(domCopy, copy);
  }
  return DOMNodeMapping(this, domCopy!, copy);
}