title: Add an image to Rmarkdown Bookdown output before top level heading
body: <p>The example below (i.e. saved as a file <code>index.rmd</code> ) has the same code chunk to display an image above and below the top level heading, but the image doesn't appear above the top level heading. This occurs if there is a file <strong>_output.yml</strong> with only this entry <code>bookdown::gitbook:</code> in the same directory. </p>
  
  <p>That line seems to enforce a table of contents (which I want) and that appears to strip out anything (image or text) before the first top level heading by default (which I don't want) - so can this behaviour be modified?</p>
  
  <pre><code>---
  site: bookdown::bookdown_site
  ---
  
  ```{r echo=FALSE, message=FALSE, warning=FALSE}
  library(imager)
  im &lt;- load.image(system.file('extdata/Leonardo_Birds.jpg',package='imager'))
  plot(im, axes=FALSE)
  ```
  
  # R Markdown
  
  ```{r echo=FALSE, message=FALSE, warning=FALSE}
  library(imager)
  im &lt;- load.image(system.file('extdata/Leonardo_Birds.jpg',package='imager'))
  plot(im, axes=FALSE)
  ```
  </code></pre>