upgrade next and add shikitwoslash to serverexternalpackages config

Author: lawreka

examples/app-router/next.config.js

@@ -1,4 +1,6 @@
 /** @type {import('next').NextConfig} */
-const nextConfig = {};
+const nextConfig = {
+    serverExternalPackages: ['@shikijs/twoslash'],
+};
 
 module.exports = nextConfig;

examples/app-router/package.json

@@ -10,9 +10,9 @@
   },
   "dependencies": {
     "@mintlify/mdx": "workspace:^",
-    "next": "14.0.4",
-    "react": "^18",
-    "react-dom": "^18"
+    "next": "15.4.2",
+    "react": "18.3.1",
+    "react-dom": "18.3.1"
   },
   "devDependencies": {
     "@tailwindcss/typography": "^0.5.10",