add popper.js

public/vendor/popper.js/packages/test-utils/utils/makeConnectedElement.js

@@ -0,0 +1,9 @@
+import makeElement from './makeElement';
+
+/**
+ * Create an element that's connected to the DOM.
+ */
+export default function makeConnectedElement() {
+  const jasmineWrapper = document.getElementById('jasmineWrapper');
+  return jasmineWrapper.appendChild(makeElement());
+}