chore(package): update css-loader to version 2.1.0

Closes #53

Author: greenkeeper[bot]

package.json

@@ -60,7 +60,7 @@
     "chalk": "^2.3.2",
     "copy-webpack-plugin": "^4.5.2",
     "coveralls": "^3.0.2",
-    "css-loader": "^0.28.0",
+    "css-loader": "^2.1.0",
     "element-ui": "^2.4.11",
     "eslint": "^5.9.0",
     "eslint-config-guo": "^0.8.0",