feat: sticky-shell (#20566)

* feat:sticky-shell

* minor-change

---------

Co-authored-by: Peer Richelsen <peeroke@gmail.com>

packages/features/shell/Shell.tsx

@@ -125,14 +125,14 @@ export default function Shell(props: LayoutProps) {
 
 export function ShellMain(props: LayoutProps) {
   const router = useRouter();
-  const { isLocaleReady, t } = useLocale();
+  const { isLocaleReady } = useLocale();
 
   return (
     <>
       {(props.heading || !!props.backPath) && (
         <div
           className={classNames(
-            "mb-0 flex items-center md:mb-6 md:mt-0",
+            "bg-default sticky top-0 z-10 mb-0 flex items-center py-2 md:mb-6 md:mt-0",
             props.smallHeading ? "lg:mb-7" : "lg:mb-8"
           )}>
           {!!props.backPath && (