message: feat(theme): update template
diff: <meta charset="utf-8" />
  <meta name="viewport" content="width=device-width,initial-scale=1" />
  <meta name="generator" content="VuePress {{ version }}" />
  + <!--vuepress-ssr-head-->
  <style>
  :root {
  --bg-color: #fff;
  document.querySelector("html").setAttribute("data-theme", "dark");
  }
  </script>
  - <!--vuepress-ssr-head-->
  - <!--vuepress-ssr-resources-->
  <!--vuepress-ssr-styles-->
  + <!--vuepress-ssr-resources-->
  </head>
  <body>
  <div id="app"><!--vuepress-ssr-app--></div>
  