docs: create Docusaurus v2.4.1 release docs + changelog (#8980)

website/versioned_docs/version-2.4.1/migration/migration-overview.mdx

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+---
+slug: /migration
+---
+
+# Migration overview
+
+This doc guides you through migrating an existing Docusaurus 1 site to Docusaurus 2.
+
+We try to make this as easy as possible, and provide a migration CLI.
+
+## Main differences {#main-differences}
+
+Docusaurus 1 is a pure documentation site generator, using React as a server-side template engine, but not loading React on the browser.
+
+Docusaurus 2, rebuilt from the ground up, generates a single-page-application, using the full power of React in the browser. It allows for more customizability but preserved the best parts of Docusaurus 1 - easy to get started, versioned docs, and i18n.
+
+Beyond that, Docusaurus 2 is a **performant static site generator** and can be used to create common content-driven websites (e.g. Documentation, Blogs, Product Landing and Marketing Pages, etc) extremely quickly.
+
+While our main focus will still be helping you get your documentations right and well, it is possible to build any kind of website using Docusaurus 2 as it is just a React application. **Docusaurus can now be used to build any website, not just documentation websites.**
+
+## Docusaurus 1 structure {#docusaurus-1-structure}
+
+Your Docusaurus 1 site should have the following structure:
+
+```bash
+├── docs
+└── website
+    ├── blog
+    ├── core
+    │   └── Footer.js
+    ├── package.json
+    ├── pages
+    ├── sidebars.json
+    ├── siteConfig.js
+    └── static
+```
+
+## Docusaurus 2 structure {#docusaurus-2-structure}
+
+After the migration, your Docusaurus 2 site could look like:
+
+```sh
+├── docs
+└── website
+    ├── blog
+    ├── src
+    │   ├── components
+    │   ├── css
+    │   └── pages
+    ├── static
+    ├── package.json
+    ├── sidebars.json
+    ├── docusaurus.config.js
+```
+
+:::info
+
+This migration does not change the `/docs` folder location, but Docusaurus v2 sites generally have the `/docs` folder inside `/website`
+
+You are free to put the `/docs` folder anywhere you want after having migrated to v2.
+
+:::
+
+## Migration process {#migration-process}
+
+There are multiple things to migrate to obtain a fully functional Docusaurus 2 website:
+
+- packages
+- CLI commands
+- site configuration
+- Markdown files
+- sidebars file
+- pages, components and CSS
+- versioned docs
+- i18n support 🚧
+
+## Automated migration process {#automated-migration-process}
+
+The [migration CLI](./migration-automated.mdx) will handle many things of the migration for you.
+
+However, some parts can't easily be automated, and you will have to fallback to the manual process.
+
+:::note
+
+We recommend running the migration CLI, and complete the missing parts thanks to the manual migration process.
+
+:::
+
+## Manual migration process {#manual-migration-process}
+
+Some parts of the migration can't be automated (particularly the pages), and you will have to migrate them manually.
+
+The [manual migration guide](./migration-manual.mdx) will give you all the manual steps.
+
+## Support {#support}
+
+For any questions, you can ask in the [`#migration-v1-to-v2` Discord channel](https://discord.gg/C3P6CxMMxY).
+
+Feel free to tag [@slorber](https://github.com/slorber) in any migration PRs if you would like us to have a look.
+
+We also have volunteers willing to [help you migrate your v1 site](https://github.com/facebook/docusaurus/issues/1834).
+
+## Example migration PRs {#example-migration-prs}
+
+You might want to refer to our migration PRs for [Create React App](https://github.com/facebook/create-react-app/pull/7785) and [Flux](https://github.com/facebook/flux/pull/471) as examples of how a migration for a basic Docusaurus v1 site can be done.