injectExtendedContextMenuItemIntoDom = function (menuItem) {
  if (!Object.keys(contextMenuExtensions).length) {
    // all menuItems appear at the bottom of the menu in their own container.
    // if this is the first extension menu we need to add the separator.
    document.getElementById('cmenu_canvas').appendChild('<li class=\'separator\'>')
  }
  const shortcut = menuItem.shortcut || ''
  document.getElementById('cmenu_canvas').appendChild(`
    <li class='disabled'><a href='#${menuItem.id}'>${menuItem.label}<span class='shortcut'>${shortcut}</span></a></li>`)
}
@param {module:contextmenu.MenuItem} menuItem
@returns {void}