Make the Tailwind Play CDN Version for Studio upgradeable from a setting

We need to be able to update the Tailwind version where needed without harming backwards compatibility. E.g. The new Flowbite Pro sections may require the 4.1.8 version for best experience.

New sites should probably be given the latest version by default, but allow it to be changed.

Existing sites should stay on their current version until it is changed.

The setting should probably be available in the Theme config (styling tab).