docs(nextjs-app - template): import assets on client (#6460)

Closes #6458

Author: Lukas742

templates/nextjs-app/app/clientAssetsImport.ts

@@ -0,0 +1,3 @@
+'use client';
+
+import '@ui5/webcomponents-react/dist/Assets';

templates/nextjs-app/app/layout.tsx

@@ -1,3 +1,4 @@
+import './clientAssetsImport.ts';
 import '@ui5/webcomponents-react/styles.css';
 import './globals.css';
 import { ThemeProvider } from '@ui5/webcomponents-react';