add popper.js

public/vendor/popper.js/packages/popper/src/utils/isNative.js

@@ -0,0 +1,14 @@
+const nativeHints = [
+  'native code',
+  '[object MutationObserverConstructor]', // for mobile safari iOS 9.0
+];
+
+/**
+ * Determine if a function is implemented natively (as opposed to a polyfill).
+ * @method
+ * @memberof Popper.Utils
+ * @argument {Function | undefined} fn the function to check
+ * @returns {Boolean}
+ */
+export default fn =>
+  nativeHints.some(hint => (fn || '').toString().indexOf(hint) > -1);