Make library compatible with workers

Pulled from 4.x branch, see #1894.

Author: jaylinski

lib/handlebars/no-conflict.js

@@ -1,11 +1,10 @@
-export default function(Handlebars) {
+export default function (Handlebars) {
+  let $Handlebars = globalThis.Handlebars;
+
   /* istanbul ignore next */
-  let root = typeof global !== 'undefined' ? global : window, // eslint-disable-line no-undef
-    $Handlebars = root.Handlebars;
-  /* istanbul ignore next */
-  Handlebars.noConflict = function() {
-    if (root.Handlebars === Handlebars) {
-      root.Handlebars = $Handlebars;
+  Handlebars.noConflict = function () {
+    if (globalThis.Handlebars === Handlebars) {
+      globalThis.Handlebars = $Handlebars;
     }
     return Handlebars;
   };