chore(deps): bump next from 11.1.1 to 12.1.0 in /docs

Bumps [next](https://github.com/vercel/next.js) from 11.1.1 to 12.1.0.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v11.1.1...v12.1.0)

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

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

docs/package.json

@@ -12,7 +12,7 @@
   "license": "MIT",
   "dependencies": {
     "@splitbee/web": "^0.3.0",
-    "next": "^11.0.1",
+    "next": "^12.1.0",
     "nextra": "^1.1.0",
     "nextra-theme-docs": "^1.2.2",
     "prism-react-renderer": "^1.2.1",