Scope sidebar nav rules to the direct child nav (#211)

The sidebar rules matched every nav inside .sidebar, so a nested
tablist nav became fixed, column, sidebar-width. Use .sidebar > nav
in the component CSS, all style packs and sidebar.js.

Co-authored-by: grugbraindev <178141691+grugbraindev@users.noreply.github.com>

src/js/sidebar.js

@@ -30,7 +30,7 @@
 
     const handleClick = (event) => {
       const target = event.target;
-      const nav = sidebarComponent.querySelector('nav');
+      const nav = sidebarComponent.querySelector(':scope > nav');
       const isMobile = window.innerWidth < breakpoint;
 
       if (isMobile && target.closest('a, button') && !target.closest('[data-keep-mobile-sidebar-open]')) {