only call highlightBlock on code element with data-lang attribute

- prevents highlight.js from logging a warning about the unknown language "none"

Author: mojavelinux

src/js/vendor/highlight.bundle.js

@@ -33,7 +33,7 @@
   //hljs.registerLanguage('swift', require('highlight.js/lib/languages/swift'))
   hljs.registerLanguage('xml', require('highlight.js/lib/languages/xml'))
   hljs.registerLanguage('yaml', require('highlight.js/lib/languages/yaml'))
-  ;[].slice.call(document.querySelectorAll('pre code.hljs')).forEach(function (node) {
+  ;[].slice.call(document.querySelectorAll('pre code.hljs[data-lang]')).forEach(function (node) {
     hljs.highlightBlock(node)
   })
 })()