docs: function injectStyles() {
    if (_stylesInjected) return;
    _stylesInjected = true;
  
    let node = doc.createElement('style');
    node.innerHTML = css;
    node.type = 'text/css';
  
    if (doc.head.childNodes.length > 0) {
      doc.head.insertBefore(node, doc.head.childNodes[0]);
    } else {
      doc.head.appendChild(node);
    }
  }