title: how to use iframe in vscode webview
body: <p>in vscode-extension webview(catcoding), i want load external webpage(like google,..),</p>
  
  <p>i tried</p>
  
  <pre><code>    panel.webview.html ="&lt;html&gt;
          &lt;meta http-equiv="refresh" content="0; url=http://www.google.com/"&gt;&lt;/meta&gt;
      &lt;/html&gt;"
  </code></pre>