docs: Add new entry to 4.0 changelog

Author: amannn

docs/src/pages/blog/next-intl-4-0.mdx

@@ -233,8 +233,9 @@ I'm particularly excited about the announcement of `rootParams`, as it seems lik
 2. Require locale to be returned from `getRequestConfig` (see [PR #1486](https://github.com/amannn/next-intl/pull/1486))
 3. Disallow passing `null`, `undefined` or `boolean` as an ICU argument (see [PR #1561](https://github.com/amannn/next-intl/pull/1561))
 4. Bump minimum required TypeScript version to 5 for projects using TypeScript (see [PR #1481](https://github.com/amannn/next-intl/pull/1481))
-5. Remove deprecated APIs (see [PR #1479](https://github.com/amannn/next-intl/pull/1479))
-6. Remove deprecated APIs pt. 2 (see [PR #1482](https://github.com/amannn/next-intl/pull/1482))
+5. Return `x-default` alternate link also for sub pages when using `localePrefix: 'always'` and update middleware matcher suggestion in docs (see [PR #1720](https://github.com/amannn/next-intl/pull/1720))
+6. Remove deprecated APIs (see [PR #1479](https://github.com/amannn/next-intl/pull/1479))
+7. Remove deprecated APIs pt. 2 (see [PR #1482](https://github.com/amannn/next-intl/pull/1482))
 
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