Update dependency webpack-dev-server to v3.4.1

Author: renovate-bot

package.json

@@ -46,6 +46,6 @@
     "typescript": "3.3.1",
     "webpack": "4.29.0",
     "webpack-cli": "3.2.1",
-    "webpack-dev-server": "3.1.14"
+    "webpack-dev-server": "3.4.1"
   }
 }