When installing Payload, `react-select` currently throws a dependency
warning because `v5.8.0` does not include React 19 in its peer deps. As
of `v5.9.0`, it now does thanks to
https://github.com/JedWatson/react-select/pull/5984.
### What?
Migrates the `form-builder` example to payload `3.0`.
`Updates`:
- Now has a next app directly along side payload.
- Removes `form-builder/next-app` & `form-builder/next-pages` example
front-ends and only uses new recommended approach (i.e admin panel &
front-end on the same port - `3000`)