title: Is it possible to freeze group headers in tabulator?
body: <p>My issue is that group headers are scrolled away when I scroll vertically. I need them to stay frozen just like the 'freeze row' option. I couldn't find a way to get the row object of group header, with which I can use the freeze option.</p>
  <p>Please guide me in the right direction.</p>
  <p>JS Code:</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>var table = new Tabulator("#example-table", {
      height:"311px",
      layout:"fitColumns",
      movableRows:true,
      groupBy:"gender",
      columns:[
          {title:"Name", field:"name", width:200},
          {title:"Progress", field:"progress", formatter:"progress", sorter:"number"},
          {title:"Gender", field:"gender"},
          {title:"Rating", field:"rating", formatter:"star", hozAlign:"center", width:100},
          {title:"Favourite Color", field:"col"},
          {title:"Date Of Birth", field:"dob", hozAlign:"center", sorter:"date"},
          {title:"Driver", field:"car", hozAlign:"center", formatter:"tickCross"},
      ],
  });</code></pre>
  </div>
  </div>
  </p>
  <p>HTML Code
  <div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div id="example-table"&gt;&lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>