<script src="https://cdn.rawgit.com/google/code-prettify/master/loader/run_prettify.js"></script>

<link rel="stylesheet" type="text/css" href="https://cdn.rawgit.com/google/code-prettify/master/loader/prettify.css">

<link rel="stylesheet" href="css/my-custom-theme-that-is-awesome.css">