title: Highcharts plotOptions.area.depth does not exist in latest version
body: <p>The HighCharts demo for 3D Area Charts: <a href="https://www.highcharts.com/demo/3d-area-multiple" rel="nofollow noreferrer">https://www.highcharts.com/demo/3d-area-multiple</a></p>
  <p>Uses <code>plotOptions.area.depth</code> to render multiple series stacked one behind another.  The latest version of HighCharts doesn't honor this setting, and the Typescript Definitions says it does not exist.  It will also throw this Error in the console:
  <code>Type ‘{ depth: number; }’ is not assignable to type ‘PlotAreaOptions’.</code></p>
  <p>How do we configure this feature now?</p>
  <p>For what it's worth, that depth setting is honored by other 3D chart types.</p>