build(deps): bump next from 15.5.18 to 15.5.22 in /docs

Bumps [next](https://github.com/vercel/next.js) from 15.5.18 to 15.5.22.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Commits](vercel/next.js@v15.5.18...v15.5.22)

---
updated-dependencies:
- dependency-name: next
  dependency-version: 15.5.22
  dependency-type: direct:production
...

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

Author: dependabot[bot]

docs/package-lock.json

@@ -15,7 +15,7 @@
   "dependencies": {
     "@stackblitz/sdk": "^1.11.0",
     "@theguild/remark-mermaid": "^0.3.0",
-    "next": "^15.5.4",
+    "next": "^15.5.22",
     "nextra": "4.2.17",
     "nextra-theme-docs": "4.2.17",
     "react": "^19.2.0",