chore(deps-dev): bump next from 13.5.7 to 15.1.2

Bumps [next](https://github.com/vercel/next.js) from 13.5.7 to 15.1.2.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v13.5.7...v15.1.2)

---
updated-dependencies:
- dependency-name: next
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

playground/nextjs/package.json

@@ -12,7 +12,7 @@
     "@types/react": "18.2.47",
     "eslint": "8.55.0",
     "eslint-config-next": "14.0.4",
-    "next": "^13.5.7",
+    "next": "^15.1.2",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
     "storyblok-js-client": "file:..",