support highlight.js

Author: yihui

exampleSite/layouts/partials/foot_custom.html

@@ -2,3 +2,11 @@
 <script defer src="//mathjax.rstudio.com/latest/MathJax.js?config=TeX-MML-AM_CHTML"></script>
 
 <script defer src="//yihui.org/js/center-img.js"></script>
+
+<script src="//cdnjs.cloudflare.com/ajax/libs/highlight.js/11.5.1/highlight.min.js"></script>
+<script src="//cdnjs.cloudflare.com/ajax/libs/highlight.js/11.5.1/languages/r.min.js"></script>
+
+<script>
+hljs.configure({languages: []});
+hljs.initHighlightingOnLoad();
+</script>

exampleSite/layouts/partials/head_custom.html

@@ -0,0 +1 @@
+<link href="//cdnjs.cloudflare.com/ajax/libs/highlight.js/11.5.1/styles/github.min.css" rel="stylesheet">