Add dropdown menu functionality

Currently the navigation menu can only be one level, i.e. you cannot have further options display below the top level - there is no simple way to create a dropdown menu.

This makes it impossible to create an intuitive, well structured menu if you have lots of sections on your blog.

Adding this would be make Ghost a viable alternative to WordPress for the millions of website owners who have limited coding skills. A proper dropdown menu is needed for any website with lots of sections, and is important to structure sites for SEO.

I don’t disagree that it’d be good to have, but for anyone finding this post, let me provide a link to a workaround that works (sometimes with minor tweaking) on many themes:
https://forum.ghost.org/t/add-dropdowns-to-main-menu-through-the-site-admin-copy-paste-into-site-header-footer-injections/

Update: with Cathy’s help I was able to create a dropdown menu, but it shows the code whilst loading, which looks weird for users and may affect trust in our site. And as shown by another user, it doesn’t work with all themes.