Update dependency webpack-cli to v4

package.json

@@ -129,7 +129,7 @@
     "webpack": "^4.41.2",
     "webpack-assets-manifest": "^3.1.1",
     "webpack-bundle-analyzer": "^3.1.0",
-    "webpack-cli": "^3.3.2",
+    "webpack-cli": "^4.0.0",
     "webpack-merge": "^5.2.0",
     "websocket.js": "^0.1.12"
   },