title: Fixed size slides in xaringan?
body: <p>I'm trying to build a presentation in <code>xaringan</code>, which uses <code>remarkjs</code>.  I'd like to make the slides all fixed-size, so they don't scale with the size of the browser. The reason is that my presentation needs to fit the format of the conference at which I'll be delivering it. </p>
  
  <p>Is there a way I can do this?  Thanks.</p>