Examine source code of Ycombinator keyboard nav

{
  "manifest_version": 2,
  "name": "Ycombinator keyboard navigation",
  "version": "3",
  "description": "Navigate ycombinator with your keyboard",
  "icons": {
    "48": "icons/48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.ycombinator.com/*"
      ],
      "js": [
        "keyboard-watcher.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{8baac415-d606-422e-89a6-2122747c54dc}"
    }
  }
}