Setup Tailwind in create-react-app project

npm install -D tailwindcss postcss autoprefixer
npx tailwindcss init -p

/** @type {import('tailwindcss').Config} */
module.exports = {
  content: [
    "./src/**/*.{js,jsx,ts,tsx}",
  ],
  theme: {
    extend: {},
  },
  plugins: [],
}

@tailwind base;
@tailwind components;
@tailwind utilities;

npm run start

export default function App() {
  return (
    <h1 className="text-3xl font-bold underline">
      Hello world!
    </h1>
  )
}