chore(deps): update dependency webpack to v4.39.1 (#297)

Author: renovate[bot]

package-lock.json

@@ -79,7 +79,7 @@
     "prettier": "1.18.2",
     "rimraf": "2.6.3",
     "standard-version": "7.0.0",
-    "webpack": "4.39.0",
+    "webpack": "4.39.1",
     "webpack-cli": "3.3.6",
     "webpack-closure-compiler": "2.1.6",
     "yargs": "13.3.0"