title: Remove background from Highchart heatmap
body: <p>I want remove the background from the highchart heatmap, as you can see in the image below i remove the highchart background but not the background inside the plot:
  <a href="https://i.stack.imgur.com/Mq1AV.png+" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Mq1AV.png+" alt="enter image description here"></a></p>
  
  <p>Anyone knows how can I achieve it?</p>
  
  <p>Thanks</p>