Dropdown drop shadow, dropped a bit from the comp

It's shifted downward to not overlap the menubar, since it's hard to make a child z-indexed below its parent.

src/components/menu/menu.css

@@ -11,6 +11,7 @@
     overflow: visible;
     color: $ui-white;
     font-weight: normal;
+    box-shadow: 0 8px 8px 0 $ui-black-transparent;
 }
 
 .menu.left {