Examine source code of FiverrAutoRefresher

{
  "manifest_version": 2,
  "name": "AutoRefresh",
  "version": "1.0",
  "description": "Refresh Firefox tabs automatically every 30 seconds!",
  "icons": {
    "48": "icons/refresh-icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.fiverr.com/*"
      ],
      "js": [
        "refresh.js"
      ]
    }
  ]
}