Fix: TouchEvent is undefined in some browsers (clauderic#382)

Author: Clauderic Demers

src/utils.js

@@ -104,7 +104,7 @@ export function getPosition(event) {
 
 export function isTouchEvent(event) {
   return (
-    event instanceof TouchEvent ||
+    event instanceof window.TouchEvent ||
     event.touches && event.touches.length ||
     event.changedTouches && event.changedTouches.length
   );