docs: create Docusaurus v2.4.0 release docs + changelog + release blog post (#8811)

website/blog/releases/2.4/index.mdx

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+---
+title: Docusaurus 2.4
+authors: [slorber]
+tags: [release]
+image: ./img/social-card.png
+date: 2023-03-23
+---
+
+We are happy to announce **Docusaurus 2.4**.
+
+The upgrade should be easy: as explained in our [release process documentation](/community/release-process), minor versions respect [Semantic Versioning](https://semver.org/).
+
+![Docusaurus blog post social card](./img/social-card.png)
+
+<!--truncate-->
+
+import BrowserWindow from '@site/src/components/BrowserWindow';
+import IframeWindow from '@site/src/components/BrowserWindow/IframeWindow';
+import ErrorBoundaryTestButton from '@site/src/components/ErrorBoundaryTestButton';
+
+## Highlights
+
+### Sidebar item description
+
+In [#8236](https://github.com/facebook/docusaurus/pull/8236), we made it possible to provide a new `description` attribute for docs sidebar items of type `link` and `category`.
+
+```tsx title="sidebars.js"
+[
+  {
+    type: 'link',
+    label: 'Link with description',
+    href: 'https://docusaurus.io',
+    // highlight-next-line
+    description: 'Some link description',
+  },
+  {
+    type: 'category',
+    label: 'Category with description',
+    // highlight-next-line
+    description: 'Some category description',
+    items: [],
+  },
+];
+```
+
+These descriptions will be used in category generated index pages.
+
+![Show sidebar category generated index with custom descriptions](./img/sidebar-item-description.jpg)
+
+### Theme Query String
+
+In [#8708](https://github.com/facebook/docusaurus/pull/8708), we added the possibility to force Docusaurus to initialize itself in `light` or `dark` mode through a new `docusaurus-theme` query-string parameter.
+
+This is useful to ensure a consistent theme when embedding an existing Docusaurus page into an iframe or WebView.
+
+<IframeWindow url="/docs/?docusaurus-theme=light" />
+<IframeWindow url="/docs/?docusaurus-theme=dark" />
+
+### Remark plugin npm2yarn upgrade
+
+In [#8690](https://github.com/facebook/docusaurus/pull/8690), we upgraded our Remark plugin [@docusaurus/remark-plugin-npm2yarn](https://github.com/facebook/docusaurus/tree/main/packages/docusaurus-remark-plugin-npm2yarn) with many conversion bug fixes, first-class support for pnpm, and the ability to register custom converters producing new tabs.
+
+````markdown
+Run these commands!
+
+```bash npm2yarn
+npm install
+npm run build
+npm run myCustomScript -- --some-arg
+```
+````
+
+<BrowserWindow>
+
+```bash npm2yarn
+npm install
+npm run build
+npm run myCustomScript -- --some-arg
+```
+
+</BrowserWindow>
+
+### gtag support for multiple tracking IDs
+
+In [#8620](https://github.com/facebook/docusaurus/pull/8620) we added support for the [@docusaurus/plugin-google-gtag](/docs/api/plugins/@docusaurus/plugin-google-gtag) plugin to declare multiple tracking IDs.
+
+```js title="docusaurus.config.js"
+module.exports = {
+  presets: [
+    [
+      '@docusaurus/preset-classic',
+      {
+        gtag: {
+          trackingID: [
+            // highlight-next-line
+            'G-<YOUR-NEW-GA4-ID>',
+            // highlight-next-line
+            'UA-<YOUR-OLD-UA-ID>',
+          ],
+        },
+      },
+    ],
+  ],
+};
+```
+
+:::caution Google is sunsetting Universal Analytics
+
+**[Google will sunset its Universal Analytics](https://blog.google/products/marketingplatform/analytics/prepare-for-future-with-google-analytics-4/)** on **July 1, 2023**.
+
+Docusaurus users should migrate to Google Analytics 4. Google **does not permit to migrate your existing Universal Analytics data** to your new Google Analytics 4 property.
+
+To preserve the continuity of your analytics, we temporarily recommend that you report events to 2 tracking IDs at the same time: the old one (`UA-*`) and new one (`G-*`). Refer to the **[dedicated issue](https://github.com/facebook/docusaurus/issues/7221)** for details.
+
+:::
+
+### Developer Experience
+
+In [#8736](https://github.com/facebook/docusaurus/pull/8736), we improved how we render error messages and added initial support to render the full causal chain of an error (see [ES2022 Error Cause](https://h3manth.com/ES2022/#error-cause)).
+
+:::tip
+
+To see it in action, click here: <ErrorBoundaryTestButton cause="Probably undefined is not a function 😄"/>
+
+:::
+
+In [#8735](https://github.com/facebook/docusaurus/pull/8735) we also made navbar-related error messages clearer to help users understand what they did wrong.
+
+![Docusaurus navbar error message screenshot](./img/navbar-error.jpg)
+
+### Translations
+
+We made it possible to translate some new elements:
+
+- [#8677](https://github.com/facebook/docusaurus/pull/8677) introduces a new `process.env.DOCUSAURUS_CURRENT_LOCALE` (experimental) allowing you to localize your config file, including site title, tagline, announcement bar, baseUrl...
+- [#8616](https://github.com/facebook/docusaurus/pull/8616) allows to translate the navbar and footer logo alt text
+
+We added default theme translation support for multiple languages:
+
+- 🇭🇺 [#8668](https://github.com/facebook/docusaurus/pull/8668): Hungarian
+- 🇳🇴 [#8631](https://github.com/facebook/docusaurus/pull/8631): Norwegian (Bokmål)
+
+:::tip
+
+Completing theme translations is an [ongoing effort](https://github.com/facebook/docusaurus/issues/3526) and an easy way to contribute to Docusaurus. We add new theme features regularly, for which we often [need new translations](https://github.com/facebook/docusaurus/issues/3526).
+
+:::
+
+## Other changes
+
+Other notable changes include:
+
+- [#8674](https://github.com/facebook/docusaurus/pull/8674): respect `prefers-reduced-motion: reduce` media query
+- [#8712](https://github.com/facebook/docusaurus/pull/8712): use a navbar item of type `docSidebar` in template
+- [#8801](https://github.com/facebook/docusaurus/pull/8801): allow tabs children to be falsy
+- [#8757](https://github.com/facebook/docusaurus/pull/8757): make search page react to external query-string changes
+- [#8803](https://github.com/facebook/docusaurus/pull/8803): fix code block buttons position in RTL
+- [#8615](https://github.com/facebook/docusaurus/pull/8615): fix color mode toggle when using dark navbar
+- [#8699](https://github.com/facebook/docusaurus/pull/8699): fix navbar dropdown tab focus bug
+
+Check the **[2.4.0 changelog entry](/changelog/2.4.0)** for an exhaustive list of changes.