Support content "sections"

Bắt đầu bằng việc xem xét các entry point makeSource và defineDocumentType được nêu trong issue, sau đó theo dõi cách các đường dẫn tài liệu và các trường được tính toán trở thành các collection như allDocsSections. So sánh các section lồng nhau được yêu cầu và metadata theo từng section với các ví dụ của Hugo và Docusaurus. Công việc được xem là hoàn tất khi API được đề xuất và cấu trúc typed đệ quy được triển khai và xác minh bằng các test phù hợp.

One of the things that I really like about Hugo is its sections feature, which enables you to separate nested directories of content into well-defined groups. So instead of a kind of "flat" array of files you end up getting a nested structure like this:

Documentation
\_ Getting started
  \_ Installation
  \_ Platforms
\_ Administration
  \_ Kubernetes
    \_ Setup
    \_ Configuration
\_ etc

As expected, sections can be infinitely nested and each can have its own metadata. I don't necessarily endorse the way that Hugo does this (you need to sprinkle _index.md files throughout your tree) but I do think that having this kind of rich structure available to you is great for creating tables of content, sidebar navs, and all of that good stuff. Personally, it's the thing that I'm missing the most as I cross the chasm from mostly doing things in Hugo to doing things in JS world.

I could envision being able to do something like this in Contentlayer:

export const Doc = defineDocumentType(() => ({
  name: 'Doc',
  filePathPattern: `**/*.md`,
  fields: {
    title: {
      type: 'string',
      description: 'The title of the doc',
      required: true,
    },
  },
  computedFields: {
    url: {
      type: 'string',
      resolve: (post) => `/docs/${post._raw.flattenedPath}`,
    },
  },
}))

export default makeSource({
  contentDirPath: 'docs',
  documentTypes: [Doc],
  // tiny little change
  sections: true,
})

This could export an allDocsSections object of type Sections<Doc> that would enable you to recurse through the tree.

<ul>
  {allDocs.sections.map(section => (
  <li>
    <p>{section.title}</p>
    
    <ul>
      {section.docs.map(doc => (
        <li>
          {doc.title}
        </li>
      ))}
      
      {section.sections.map(section => ( /* nest */ ))}
    </ul>
  </li>)}
</ul>

This is very off the cuff but hopefully provides some sense of what I'm suggesting. I'd be quite happy to help out with this if others find the idea compelling. Just wanted to register it here in this forum.

Note: Docusaurus also supports this using a _category_.{json|yml} file that creates a new "category" (basically an analogue to the sections concept) wherever it's found in the directory tree.