chore(package): update css-loader to version 3.4.0

Author: greenkeeper[bot]

package.json

@@ -20,7 +20,7 @@
     "autoprefixer": "9.7.3",
     "clean-webpack-plugin": "3.0.0",
     "cross-env": "6.0.3",
-    "css-loader": "3.3.2",
+    "css-loader": "3.4.0",
     "mini-css-extract-plugin": "0.8.1",
     "postcss-loader": "3.0.0",
     "sass": "1.23.7",