Adding correct version of webpack CLI

Author: nicolasgarnier

example/package.json

@@ -24,7 +24,8 @@
     "extract-text-webpack-plugin": "^4.0.0-beta.0",
     "firebase-tools": "^5.0.0",
     "style-loader": "^0.21.0",
-    "webpack": "^4.8.3"
+    "webpack": "^4.8.3",
+    "webpack-cli": "^3.0.0"
   },
   "private": true
 }

package.json

@@ -66,6 +66,6 @@
     "react": "^16.3.2",
     "style-loader": "^0.21.0",
     "webpack": "^4.8.3",
-    "webpack-cli": "^2.1.3"
+    "webpack-cli": "^3.0.0"
   }
 }