fix(package): update webpack to version 4.0.0

Author: greenkeeper[bot]

package.json

@@ -37,7 +37,7 @@
     "json-format": "^1.0.1",
     "lodash": "^4.17.5",
     "swagger-client": "^3.4.7",
-    "webpack": "^3.10.0"
+    "webpack": "^4.0.0"
   },
   "engines": {
     "node": ">=8.4.0"