Add supporting themes required for Lotusdocs

themes/hugo-mod-jslibs-dist/popperjs/package/dist/esm/dom-utils/getDocumentElement.js

@@ -0,0 +1,6 @@
+import { isElement } from "./instanceOf.js";
+export default function getDocumentElement(element) {
+  // $FlowFixMe[incompatible-return]: assume body is always available
+  return ((isElement(element) ? element.ownerDocument : // $FlowFixMe[prop-missing]
+  element.document) || window.document).documentElement;
+}