title: Prism.js syntax highighting not working
body: <p>I'm using Docsify to serve documentation about my project.
  For the syntax highlighting I want to use prism.js. Sadly, the highlighting part does not work. I've also tried all the suggestions mentioned <a href="https://stackoverflow.com/questions/18391425/markup-not-showing-up-using-prism-js">here</a>.</p>
  
  <p>In my index.html I have <code>&lt;script src="//unpkg.com/prismjs/components/prism-ruby.js"&gt;&lt;/script&gt;</code> included, as docsify mentioned <a href="https://docsify.js.org/#/language-highlight" rel="nofollow noreferrer">here</a>. And in my <code>file.md</code> where I want to show some Ruby code:</p>
  
  <pre><code>&lt;pre&gt;&lt;code class="language-ruby"&gt;
    def hello(name)
      p "Hello #{name}"
    end
  &lt;/code&gt;&lt;/pre&gt;
  </code></pre>
  
  <p>But the Ruby code is not being highlighted.
  <a href="https://i.stack.imgur.com/wVpYg.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/wVpYg.png" alt="enter image description here"></a>  </p>
  
  <p>HTML being rendered: </p>
  
  <pre><code>&lt;pre&gt;&lt;code class="language-ruby"&gt;
    def hello(name)
      p "Hello #{name}"
    end
  &lt;/code&gt;&lt;/pre&gt;
  </code></pre>
  
  <p>What am I missing here?</p>