• [x ] I have checked the latest main branch to see if this has already been fixed
• [ x] I have searched existing issues and pull requests for duplicates

URL to the section(s) of the book with this problem: any

Description of the problem:

Opening the menu in mobile Safari allows the main content to still be scrolled around. It seems the overflow is not being hidden.

Safari on iOS 15.0.1

Screencast: https://streamable.com/muvl31

Suggested fix: