chore(deps): update dependency webpack-dev-server to v3.9.0

Author: renovate-bot

package.json

@@ -36,6 +36,6 @@
     "vue-loader": "15.6.4",
     "vue-style-loader": "4.1.2",
     "webpack": "4.29.5",
-    "webpack-dev-server": "3.1.14"
+    "webpack-dev-server": "3.9.0"
   }
 }