Force Tailwind to include some classes in build phase

As suggested by Ihar Aliakseyenka, the “safelist” section is exactly what I was looking for. Thanks Ihar!

module.exports = {
  content: [
    './pages/**/*.{html,js}'
    './components/**/*.{html,js}',
  ],
  safelist: [
    'bg-red-500',
    'text-3xl',
    'lg:text-4xl',
  ]
  // ...
}