Tweak package.json for fetch example

Author: alexcrichton

examples/fetch/package.json

@@ -1,10 +1,11 @@
 {
   "scripts": {
-    "serve": "webpack-serve ./webpack.config.js"
+    "serve": "webpack-dev-server"
   },
   "devDependencies": {
     "html-webpack-plugin": "^3.2.0",
-    "webpack": "^4.16.5",
-    "webpack-serve": "^2.0.2"
+    "webpack": "^4.11.1",
+    "webpack-cli": "^2.0.10",
+    "webpack-dev-server": "^3.1.0"
   }
 }