docs: general design fixes (#2545)

* general fixes to the docs design

* fix condition checking for auto color scheme

www/docs/src/css/_sidebar.css

@@ -236,4 +236,8 @@ html:not([data-theme="dark"]) .menu__list-item.topright-icon .menu__link.menu__l
 
 .navbar-github-link {
   overflow: visible;
+}
+
+.sidebar-desktop:not(.scrolling) nav::-webkit-scrollbar {
+  --ifm-scrollbar-size: 0px;
 }