chore(package): update webpack-dev-server to version 3.1.4

Author: greenkeeper[bot]

package.json

@@ -109,7 +109,7 @@
     "typescript": "2.4.2",
     "webpack": "4.6.0",
     "webpack-dev-middleware": "3.1.3",
-    "webpack-dev-server": "3.1.3",
+    "webpack-dev-server": "3.1.4",
     "yargs": "11.0.0",
     "zone.js": "0.8.26"
   },