Added Element extension with .matches and .closest

app/assets/javascripts/extensions/element.js.es6

-/* eslint-disable */
-Element.prototype.matches = Element.prototype.matches || Element.prototype.msMatches;
+/* global Element */
+/* eslint-disable consistent-return, max-len */
+
+Element.prototype.matches = Element.prototype.matches || Element.prototype.msMatchesSelector;
 Element.prototype.closest = function closest(selector, selectedElement = this) {
   if (!selectedElement) return;