fix(deps): update dependency next to v15

Author: renovate[bot]

package.json

@@ -12,7 +12,7 @@
   "dependencies": {
     "diff": "5.1.0",
     "lz-string": "1.5.0",
-    "next": "13.4.19",
+    "next": "15.4.3",
     "react": "18.2.0",
     "react-dom": "18.2.0",
     "tailwindcss": "3.3.3"