Hotfix for broken test for dates

Fixes #9726

boot/boot.js

@@ -47,6 +47,13 @@ $tw.utils.hop = function(object,property) {
 /** @deprecated Use Array.isArray instead  */
 $tw.utils.isArray = (value) => Array.isArray(value);
 
+/*
+Determine if a value is a date, even across VM boundaries
+*/
+$tw.utils.isDate = function(value) {
+	return Object.prototype.toString.call(value) === "[object Date]";
+};
+
 /*
 Check if an array is equal by value and by reference.
 */