Mention hapi's major upgrade

Author: danyalaytekin

Diff for: CHANGELOG.md

@@ -6,6 +6,7 @@
 * **Major** Upgrade to `pa11y@^8` from `^6`
   * Includes an upgrade to Puppeteer `^22` from `9`.
   * Fixes compatibility with Ubuntu versions 20.04 and above. The [workaround](MIGRATION.md#migrating-from-30-to-40) documented for `pa11y-webservice@4` is no longer required.
+* **Major** Upgrade to `hapi@21` from `20`
 * Upgrade to `[email protected]` from `3.0`
 
 Full comparison to `4.3.1`: [4.3.1...5.0.0](https://github.com/pa11y/pa11y/compare/4.3.1...5.0.0)