form-cheatsheet/postcss.json

{
  "use": ["autoprefixer", "postcss-css-variables", "cssnano"],
  "input": "css/src/style.css",
  "output": "css/style.min.css",
  "autoprefixer": {
    "browsers": "> 1%"
  },
  "cssnano": {
    "autoprefixer": false
  },
  "postcss-css-variables": {
    "preserve": true
  }
}