message: Add 'test' command.
diff: "dev": "next dev",
  "build": "next build",
  "start": "next start",
  - "preview": "yarn build && next export && npx http-server out/ -p 3000"
  + "preview": "yarn build && next export && npx http-server out/ -p 3000",
  + "test": "jest"
  }
  }
  