title: Display contents of a file with code using markdown and revealjs
body: <p>I am writing a presentation in a markdown file referenced by Reveal.JS.
  I would like to import external file's source code in a markdown code block without having to do copy &amp; paste. Ideally I would like to put a relative path to the file like I can do with an image.</p>
  
  <p>Is it supported? I couldn't find it mentioned in the documentation.</p>
  
  <p>Thanks.</p>