Update webpack-dev-server

Author: ianberryman

package.json

@@ -106,7 +106,7 @@
     "style-loader": "^1.2.1",
     "webpack": "^4.44.1",
     "webpack-cli": "^3.3.12",
-    "webpack-dev-server": "^3.11.0",
+    "webpack-dev-server": "^4.9.1",
     "webpack-manifest-plugin": "2.2.0",
     "workbox-webpack-plugin": "4.3.1"
   },