Need Vanilla JS toggle

I have a site here:
https://treasuretown.gallery/

If you click on the "?????" at the bottom it toggles the about page. Right now it uses jQuery but I'd rather not have that dependency. It's simple enough that I don't think we need jQuery.

Can someone give me the code to replace this jQuery code:
$(document).ready(function () {
$(".toggle").click(function () {
$(".about").toggleClass("about-up about-down");
});
});