chore(v2): prepare v2.0.0-beta.1 release (#5004)

* beta.1

* v2.0.0-beta.1

website/versioned_docs/version-2.0.0-beta.1/guides/docs/docs-introduction.md

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+---
+id: introduction
+title: Docs Introduction
+sidebar_label: Introduction
+slug: /docs-introduction
+---
+
+The docs feature provides users with a way to organize Markdown files in a hierarchical format.
+
+## Document ID {#document-id}
+
+Every document has a unique `id`. By default, a document `id` is the name of the document (without the extension) relative to the root docs directory.
+
+For example, `greeting.md` id is `greeting` and `guide/hello.md` id is `guide/hello`.
+
+```bash
+website # Root directory of your site
+└── docs
+   ├── greeting.md
+   └── guide
+      └── hello.md
+```
+
+However, the **last part** of the `id` can be defined by user in the front matter. For example, if `guide/hello.md`'s content is defined as below, its final `id` is `guide/part1`.
+
+```yml
+---
+id: part1
+---
+Lorem ipsum
+```
+
+If you want more control over the last part of the document URL, it is possible to add a `slug` (defaults to the `id`).
+
+```yml
+---
+id: part1
+slug: part1.html
+---
+Lorem ipsum
+```
+
+:::note
+
+It is possible to use:
+
+- absolute slugs: `slug: /mySlug`, `slug: /`...
+- relative slugs: `slug: mySlug`, `slug: ./../mySlug`...
+
+:::
+
+## Home page docs {#home-page-docs}
+
+If you want a document to be available at the root, and have a path like `https://docusaurus.io/docs/`, you can use the slug frontmatter:
+
+```yml
+---
+id: my-home-doc
+slug: /
+---
+Lorem ipsum
+```
+
+## Docs-only mode {#docs-only-mode}
+
+If you only want the documentation feature, you can run your Docusaurus 2 site without a landing page and display your documentation page as the index page instead.
+
+To enable docs-only mode, set the docs plugin `routeBasePath: '/'`, and use the frontmatter `slug: /` on the document that should be the index page ([more infos](#home-page-docs)).
+
+:::caution
+
+You should delete the existing homepage at `./src/pages/index.js`, or else there will be two files mapping to the same route!
+
+:::
+
+:::tip
+
+There's also a "blog-only mode" for those who only want to use the blog feature of Docusaurus 2. You can use the same method detailed above. Follow the setup instructions on [Blog-only mode](../../blog.md#blog-only-mode).
+
+:::