Add supporting themes required for Lotusdocs

themes/hugo-mod-jslibs-dist/popperjs/package/lib/dom-utils/instanceOf.js.flow

@@ -0,0 +1,29 @@
+// @flow
+import getWindow from './getWindow';
+
+declare function isElement(node: mixed): boolean %checks(node instanceof
+  Element);
+function isElement(node) {
+  const OwnElement = getWindow(node).Element;
+  return node instanceof OwnElement || node instanceof Element;
+}
+
+declare function isHTMLElement(node: mixed): boolean %checks(node instanceof
+  HTMLElement);
+function isHTMLElement(node) {
+  const OwnElement = getWindow(node).HTMLElement;
+  return node instanceof OwnElement || node instanceof HTMLElement;
+}
+
+declare function isShadowRoot(node: mixed): boolean %checks(node instanceof
+  ShadowRoot);
+function isShadowRoot(node) {
+  // IE 11 has no ShadowRoot
+  if (typeof ShadowRoot === 'undefined') {
+    return false;
+  }
+  const OwnElement = getWindow(node).ShadowRoot;
+  return node instanceof OwnElement || node instanceof ShadowRoot;
+}
+
+export { isElement, isHTMLElement, isShadowRoot };