message: add start script
diff: "design-system"
  ],
  "author": "GitHub, Inc.",
  + "contributors": [
  + {
  + "name": "Diana Mounter",
  + "email": "diana.mounter@gmail.com"
  + }
  + ],
  "license": "MIT",
  "bugs": {
  "url": "https://github.com/primer/primer-react/issues"
  "react": "^16.2.0",
  "styled-components": "^3.1.6",
  "styled-system": "^2.0.2"
  + },
  + "scripts": {
  + "start": "x0 dev src/Index.js -op 8888"
  }
  }
  