[mitulkheni]

Adds a section to the scrolling overview that shows how to listen to scroll events with cdkScrollable and the ScrollDispatcher, along with a live example.

Fixes #9594
The scrolling overview only had two short paragraphs about cdkScrollable and ScrollDispatcher and didn't show how to actually listen to scroll events. This adds:

• a section on elementScrolled, scrolled and ancestorScrolled, with a snippet
• a live example (cdk-scrollable-overview) that shows the scroll offset and scrolls back to the top
• a note that the events fire outside the Angular zone, so the view only updates if you use signals or markForCheck