title: Change the chartArea background color of gvisAnnotationChart
body: <p>How to change the chartArea background color of gvisAnnotationChart?</p>
  <p>I tried this but didn't work (I tried to replicate what I saw in <a href="https://stackoverflow.com/questions/39135372/change-border-background-in-google-charts-annotationchart/39138141#39138141">this answer)</a></p>
  <pre><code>gvisAnnotationChart(
  ...,
  options = list(
      ...,
      chart = list(
        backgroundColor = &quot;#D3D3D3&quot;
      )
    )
  )
  </code></pre>