chore: Header docz page examples (#1586)

* Creating Header example

* Improve NavBag example page

* Fixing callouts

platform/ui/src/components/NavBar/NavBar.jsx

@@ -6,7 +6,7 @@ const NavBar = ({ className, children }) => {
   return (
     <div
       className={classnames(
-        'flex flex-row items-center bg-custom-navy px-3 py-1 sticky top-0 z-10',
+        'flex flex-row items-center bg-custom-navy px-3 py-1 sticky top-0 z-10 border-b-4 border-black',
         className
       )}
     >