[Learn] Table of contents widget

[huyenltnguyen]

Description

The FSD review page can be quite long, so I think we might want to add a "Table of Contents" widget to allow campers to jump to sections quickly.

I'm not sure where the widget should be in the UI. It has to be accessible at any scrolling position, so I think it could be a menu that is wired to a FloatingActionButton. Or maybe we can put it in an end drawer (https://api.flutter.dev/flutter/material/Scaffold/endDrawer.html)?

Examples

• Module review page: https://www.freecodecamp.org/learn/full-stack-developer/review-html-accessibility/review-html-accessibility
• Chapter review page: https://www.freecodecamp.org/learn/full-stack-developer/review-html/review-html