chore(examples): Add vanilla-extract example (vercel#41061)

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have a helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have a helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `pnpm lint`
- [ ] The "examples guidelines" are followed from [our contributing doc](https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md)


Response to vercel#29165


Co-authored-by: Balázs Orbán <18369201+balazsorban44@users.noreply.github.com>

examples/with-vanilla-extract/README.md

@@ -0,0 +1,3 @@
+# Next.js + vanilla-extract Example
+
+The official vanilla-extract repository maintains an example in [examples/next](https://github.com/vanilla-extract-css/vanilla-extract/tree/master/examples/next)