chore(package): update @types/webpack to version 4.39.1

Author: greenkeeper[bot]

package.json

@@ -27,7 +27,7 @@
     "@types/react-test-renderer": "^16.8.1",
     "@types/sinon": "^7.0.12",
     "@types/sinon-chai": "^3.2.2",
-    "@types/webpack": "^4.4.32",
+    "@types/webpack": "^4.39.1",
     "coveralls": "^3.0.3",
     "fork-ts-checker-webpack-plugin": "^1.3.4",
     "happypack": "^5.0.1",