chore(package): update webpack to version 4.12.0

Author: greenkeeper[bot]

package.json

@@ -60,7 +60,7 @@
     "release-it": "^7.2.1",
     "rimraf": "^2.6.2",
     "sinon": "^6.0.0",
-    "webpack": "^4.8.3",
+    "webpack": "^4.12.0",
     "webpack-cli": "^3.0.4"
   },
   "dependencies": {