added build:prod script

added production build script

package.json

@@ -5,6 +5,7 @@
     "ng": "ng",
     "start": "ng serve --host 0.0.0.0 --port 4200",
     "build": "ng build --base-href /next/ --aot --delete-output-path",
+    "build:prod": "ng build --configuration production --base-href /next/ --aot --delete-output-path",
     "watch": "ng build --watch --configuration development",
     "test": "ng test"
   },