title: Markdown: Change default font size of code chunks in ioslides
body: <p>I am trying to change the font size of a code chunk (more precisely I want to use a smaller font).
  Take the following basic example:</p>
  
  <pre><code>---
  title: "Example"
  output:
    ioslides_presentation:
    toc: yes
  widescreen: yes
  ---
  
  ## Code
  
  ```{r, eval=FALSE}
  print(mtcars)
  ```
  </code></pre>
  
  <p>Anyone an idea? Is there a YAML option like code-font-size or something like that?</p>