Update README to reflect Tailwind 4 update

Author: l2dy

templates/rescript-template-vite/README.md

@@ -7,7 +7,7 @@ This is a Vite-based template with following setup:
 - [ReScript](https://rescript-lang.org) 11.0 with @rescript/react, [Core](https://github.com/rescript-association/rescript-core) and JSX v4
 - ES6 modules (ReScript code compiled to `.res.mjs` files)
 - Vite 4 with React Plugin (Fast Refresh)
-- Tailwind 3
+- Tailwind 4
 
 ## Development