Add support for displaying articles based on directory structure for documentation

Issue Checklist

• I am using NexT version 8.0 or later.
• I have already read the Troubleshooting page of Hexo and Troubleshooting page of NexT.
• I have already searched for current issues, which does not help me.

Expected behavior

我想把文档全部迁移过来, 把gitbook 迁移到hexo + next 的系统.

现在面临一个问题, 对于文档, 我想在左边的导航栏里, 生成文档的目录树, 类似 https://oceanbase.github.io/, 或者
https://zalando-incubator.github.io/hexo-theme-doc/usage-and-configuration/swagger/introduction.html

我不想用2个系统分别来生成blog 和document, 有没有办法一个系统来生成.

因为next 很好集成了 大量的插件, 尤其是搜索插件和评论插件, 这个对我们来说很方便.

Actual behavior

• Links to demo site with this issue:
• Links to repository or source code of the blog:
• Screenshots:

Steps to reproduce the behavior

请问如何可以实现 https://zalando-incubator.github.io/hexo-theme-doc/usage-and-configuration/swagger/introduction.html

Other Information

No response

Start by reviewing the linked OceanBase and Zalando documentation examples and the theme's existing navigation and article-generation entry points. The issue names no files or tests; done would require a decided, documented approach for generating a directory-tree sidebar while keeping blog and documentation content in one Hexo site.