title: how to use the plantUML preview in VSCode?
body: <p>I am trying to use plantuml add-ons on VSCode: there are several but none of them is working.
  In this eample I am using the plantUML add-on.</p>
  <p><a href="https://i.stack.imgur.com/o27Y0.png" rel="noreferrer"><img src="https://i.stack.imgur.com/o27Y0.png" alt="the extension I am using" /></a></p>
  <p><a href="https://i.stack.imgur.com/T0S2t.png" rel="noreferrer"><img src="https://i.stack.imgur.com/T0S2t.png" alt="My VSCode" /></a></p>
  <p>As you can see on the second image the preview is blank.</p>
  <p>Can you help me ?</p>