Make @tailwindcss/jit default engine for Tailwind CSS (#23192)

This Pull Request makes [`@tailwindcss/jit`](https://github.com/tailwindlabs/tailwindcss-jit) the default engine for Tailwind CSS.

It has the following advantages:
- Lightning-fast build times because the CSS is generated on demand.
- Every variant is enabled out of the box.
- Generate arbitrary styles without writing custom CSS.
- Better performance in browser dev-tools.

examples/with-tailwindcss/README.md

@@ -2,6 +2,8 @@
 
 This example shows how to use [Tailwind CSS](https://tailwindcss.com/) (v2) with Next.js. It follows the steps outlined in the official [Tailwind docs](https://tailwindcss.com/docs/guides/nextjs).
 
+It uses the new [`@tailwindcss/jit`](https://github.com/tailwindlabs/tailwindcss-jit) engine for Tailwind CSS.
+
 ## Deploy your own
 
 Deploy the example using [Vercel](https://vercel.com?utm_source=github&utm_medium=readme&utm_campaign=next-example):

examples/with-tailwindcss/package.json

@@ -13,6 +13,7 @@
     "react-dom": "^17.0.1"
   },
   "devDependencies": {
+    "@tailwindcss/jit": "0.1.3",
     "autoprefixer": "^10.0.4",
     "postcss": "^8.1.10",
     "tailwindcss": "^2.0.2"

examples/with-tailwindcss/postcss.config.js

@@ -2,7 +2,7 @@
 // https://tailwindcss.com/docs/using-with-preprocessors
 module.exports = {
   plugins: {
-    tailwindcss: {},
+    '@tailwindcss/jit': {},
     autoprefixer: {},
   },
 }