fix: tailwind compiled string path

[cossssmin]

This PR fixes an issue where providing a pre-compiled CSS string in order to skip Tailwind CSS compilation was not working because we were checking for it in the wrong place.

You may now do this in your Maizzle config.js if you want to skip Tailwind CSS compilation:

module.exports = {
  build: {
    tailwind: {
      compiled: '',
    }
  }
}