feat(next): add script for local prod start

Because:

- Easily start payments-next in a prod like fashion.

This commit:

- Add a script to payments-next to start the application in a similar
  fashion to how it would be run in a deployed environment.

Closes #PAY-3489

Author: StaberindeZA

apps/payments/next/project.json

@@ -33,6 +33,10 @@
       },
       "dependsOn": ["glean-lint"]
     },
+    "start-prod-local": {
+      "command": "npm start --prefix apps/payments/next -- -p 3035",
+      "dependsOn": ["build", "delete"]
+    },
     "start": {
       "command": "pm2 start apps/payments/next/pm2.config.js && yarn check:url localhost:3035/__heartbeat__",
       "dependsOn": ["l10n-bundle", "glean-generate"]