fix: Select all menus by using querySelectorAll to add event listeners to each button

I have the same markup for 4 `` elements on the page, and right now my JavaScript is using `querySelector` for the first button and first nav ul on the page. I'll need all of them so that I can listen for clicks and add a different class for each nav menu.

Start by locating the JavaScript that currently uses querySelector for the header button and nav ul. Verify that all four headers receive click listeners and that each click applies a distinct class to its corresponding navigation menu.

Written by the indexing model from the issue text.