chore(package): update url-loader to version 4.0.0

Closes #31

Author: greenkeeper[bot]

package.json

@@ -70,7 +70,7 @@
     "rimraf": "^2.6.2",
     "sass-loader": "^7.1.0",
     "style-loader": "^0.23.1",
-    "url-loader": "^1.1.2",
+    "url-loader": "^4.0.0",
     "webpack": "^4.20.2",
     "webpack-cli": "^3.1.2",
     "webpack-dev-server": "^3.1.9",