function addRow(gui, newDom, liBefore) {
  const li = document.createElement('li');
  if (newDom) {
    li.appendChild(newDom);
  }

  if (liBefore) {
    gui.__ul.insertBefore(li, liBefore);
  } else {
    gui.__ul.appendChild(li);
  }
  gui.onResize();
  return li;
}
Add a row to the end of the GUI or before another row.

@param gui
@param [newDom] If specified, inserts the dom content in the new row
@param [liBefore] If specified, places the new row before another row

@ignore