fix: fix notification banner display when too much items in chat list (…

…#1593)

Issue: #1578

Demo
<img width="1512" alt="Screenshot 2023-11-06 at 14 26 14"
src="https://github.com/StanGirard/quivr/assets/63923024/ef583683-43da-4b42-927e-22431cbeb0cf">

frontend/app/chat/layout.tsx

@@ -24,7 +24,7 @@ const Layout = ({ children }: LayoutProps): JSX.Element => {
       <ChatsProvider>
         <ChatProvider>
           <NotificationBanner />
-          <div className="relative h-full w-full flex justify-stretch items-stretch">
+          <div className="relative h-full w-full flex justify-stretch items-stretch overflow-auto">
             <ChatsList />
             {children}
           </div>