docs(website): use .mdx extension for every docs

[slorber]

Motivation

As part of the MDX 2 migration (#8288)

We want MDX docs to have the .md extension

If you want to use CommonMark (which we don't for our own website here), you could still use .md extension.

Using MDX syntax with the .md extension (like many Docusaurus sites do historically) is problematic for tooling integration (IDE, Prettier etc...)

How to migrate

Change file extensions

On macos:

brew install rename
find docs -type f -name "*.md" -exec rename 's/\.md$/.mdx/' '{}' \;
find versioned_docs -type f -name "*.md" -exec rename 's/\.md$/.mdx/' '{}' \;
find blog -type f -name "*.md" -exec rename 's/\.md$/.mdx/' '{}' \;

You should find a similar alternative for your own OS to automate this.

Change Markdown links

We want:

• [link](doc.md) => [link](doc.mdx)
• [link](doc.md#anchor) => [link](doc.mdx#anchor)
• [link](https://github.com/facebook/docusaurus/blob/main/README.md) => [link](https://github.com/facebook/docusaurus/blob/main/README.md) (not updated on purpose because absolute URL)

With IntelliJ regexp replace:

• From: \((?<url>(?!http)[^ ]*?)(?<ext>\.md)(?<hash>#[^ ]+)?\)
• To: (${url}.mdx${hash})

You can probably do a similar thing with your own IDE or CLI tools.

If you need something more reliable than a regexp because of a few edge cases, you can try writing a Remark plugin to parse Markdown and process its links with a visitor.

i18n notes

.md files on Crowdin should be renamed to .mdx

In practice it's not really possible to change a file extension on Crowdin, but you should be able to re-upload .mdx files, and then delete .md files and translations should not be lost if you use Crowdin settings for String Deduplication:

Test Plan

preview

Test links

Deploy preview: https://deploy-preview-8490--docusaurus-2.netlify.app/

Related issues/PRs

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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	PWA	Report
/	🟢 94	🟢 97	🟢 100	🟢 100	🟢 90	Report
/docs/installation	🟠 80	🟢 100	🟢 100	🟢 100	🟢 90	Report

[github-actions]

Size Change: +253 B (0%)

Total Size: 889 kB

Filename	Size	Change
website/build/assets/js/main.********.js	665 kB	+253 B (0%)

ℹ️ View Unchanged

Filename	Size
website/.docusaurus/globalData.json	71 kB
website/build/assets/css/styles.********.css	112 kB
website/build/index.html	40.9 kB

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