renderLitAsNode = litHtmlTemplate => {
  const offlineRenderContainer = document.createElement('div');
  render(litHtmlTemplate, offlineRenderContainer);
  return offlineRenderContainer.firstElementChild;
}
Helper to render a lit TemplateResult as an offline-created DOM node
Make sure that the top-most element in the template has no siblings,
as they won't be taken into account. We only return firstElementChild.
@param {import('lit').TemplateResult} litHtmlTemplate