message: Removed CustomEvents polyfill
diff: -// CustomEvent
  -if (window && !window.CustomEvent) {
  - let CustomEvent = (event, params) => {
  - params = params || {bubbles: false, cancelable: false, detail: undefined};
  - let evt = document.createEvent('CustomEvent');
  - evt.initCustomEvent(event, params.bubbles, params.cancelable, params.detail);
  - return evt;
  - };
  -
  - CustomEvent.prototype = window.Event.prototype;
  -
  - window.CustomEvent = CustomEvent;
  -}
  -
  // Element.prototype.closest
  if (window) {
  window.Element.prototype.closest = window.Element.prototype.closest || function (css) {
  