title: Option to format/indent code in Highlight.js
body: <p>How do you make highlight.js auto format the code? Is there an option or function? I am passing in a string like the below:</p>
  <pre><code>&amp;lt;div&amp;gt; &amp;lt;p&amp;gt; foo &amp;lt;/p&amp;gt; &amp;lt;/div&amp;gt;
  </code></pre>
  <p>And I am trying obtain the following output with the HTML auto-formatted:</p>
  <pre><code>&lt;div&gt;
    &lt;p&gt;foo&lt;/p&gt;
  &lt;/div&gt;
  </code></pre>
  <p>Full code:</p>
  <pre><code>&lt;pre id=&quot;output&quot;&gt;&lt;code&gt;  &amp;lt;div&amp;gt; &amp;lt;p&amp;gt; foo &amp;lt;/p&amp;gt; &amp;lt;/div&amp;gt; &lt;/code&gt;&lt;/pre&gt;
  
  &lt;script&gt;hljs.highlightBlock($('#output')[0]);&lt;/script&gt;
  </code></pre>