mergeNearStringNodes method
Implementation
DOMNodeMapping<T>? mergeNearStringNodes(DOMNode domNode1, DOMNode domNode2,
    {bool onlyCompatibles = false}) {
  if (domNode1.isStringElement && domNode2.isStringElement) {
    return mergeNearNodes(domNode1, domNode2,
        onlyCompatibles: onlyCompatibles);
  }
  return null;
}