fixup! Move default highlight.js highlighting into a web worker

Author: Steve Day

public/js/highlight-worker.js

@@ -1,7 +1,10 @@
 // A very simple web worker for highlight.js
 // See: https://highlightjs.org/usage/
+'use strict';
+
+importScripts('/vendor/plugins/highlight/highlight.pack.js');
+
 onmessage = function(event) {
-    importScripts('/vendor/plugins/highlight/highlight.pack.js');
     var result = self.hljs.highlightAuto(event.data.text);
     postMessage({index: event.data.index, html: result.value});
 };