feat(client): add admin comment badge for client

[lizheming]

fix #115

The default badge text is Admin, If you want to custom text, you can set langMode.admin property like following:

Waline({
  el: '#comments',
  serverURL: 'xxx',
  langMode: {
    admin: 'God'
  }
});

---

默认角标文案是 博主。你可以设置 langMode.admin 字段来自定义文案：

Waline({
  el: '#comments',
  serverURL: 'xxx',
  langMode: {
    admin: '玉皇大帝'
  }
});