docs(website): add missing "which" and "the"

* "the": because the PageElements API is a specific one, we preface it with the definite article "the".
* "which": the relative pronoun "which" is necessary here to help the user know what we're referring to.

Refs: https://gallaudet.edu/student-success/tutorial-center/english-center/grammar-and-vocabulary/definite-and-indefinite-articles/a-an-the-general-or-specific/
Refs: https://www.wm.edu/as/wcc/newresources/handouts/using-that-which-who.pdf

Author: TurekBot

src/docs/handbook/web-testing/page-element-query-language.md

@@ -494,7 +494,7 @@ Of course, you can set your own description if you prefer using `.describedAs()`
 
 You might have also noticed that the [`childElement.of(parentElement)`](/api/web/class/PageElement/#of) API
 works only with **individual elements**.
-To map **multiple elements** we need to use `PageElements` [mapping API](/handbook/web-testing/page-element-query-language/#mapping-page-elements-in-a-collection) we'll talk about next.
+To map **multiple elements** we need to use the `PageElements` [mapping API](/handbook/web-testing/page-element-query-language/#mapping-page-elements-in-a-collection), which we'll talk about next.
 
 :::tip Serenity/JS PEQL helps you avoid code duplication
 Serenity/JS PEQL lets you **compose** and **reuse** page element definitions,