doc: add String.prototype.at and %TypedArray%.prototype.at

PR-URL: #39583
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Beth Griggs <bgriggs@redhat.com>
Reviewed-By: Ash Cripps <acripps@redhat.com>

doc/changelogs/CHANGELOG_V16.md

@@ -99,7 +99,7 @@ This is a security release.
 
 The V8 engine is updated to version 9.2.230.21.
 
-It notably introduces the new [`Array.prototype.at`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/at) method:
+It notably introduces the new [`Array.prototype.at`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/at) method (also on [Typed Arrays](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/at) and [strings](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/at)):
 
 ```js
 const array = [1, 2, 3];