chore: fix css minimize

package.json

@@ -38,6 +38,7 @@
     "babel-loader": "^8.0.6",
     "cross-env": "^5.2.0",
     "css-loader": "^2.1.1",
+    "cssnano": "^4.1.10",
     "eslint": "^5.16.0",
     "eslint-loader": "^2.1.2",
     "exports-loader": "^0.7.0",

webpack/postcss.config.js

@@ -1,5 +1,6 @@
 module.exports = {
     plugins: {
-        'autoprefixer': {}
+        'autoprefixer': {},
+        'cssnano': {}
     }
 };

webpack/prod.config.js

@@ -62,7 +62,6 @@ module.exports = {
                         loader: 'css-loader',
                         options: {
                             importLoaders: 1,
-                            minimize: true,
                             sourceMap: true
                         }
                     },