Examine source code of RocketLink

{
  "manifest_version": 2,
  "name": "RocketLink.io - Track any link you share",
  "description": "RocketLink lets you add retargeting pixels to any link you share. Anyone who clicks on your link will turn into the custom audience.",
  "version": "1.4resigned1",
  "browser_action": {
    "default_icon": "images/rocketlink-logo-32.png",
    "default_popup": "config.html"
  },
  "permissions": [
    "https://app.rocketlink.io/*",
    "activeTab",
    "tabs"
  ],
  "icons": {
    "16": "images/rocketlink-logo-16.png",
    "32": "images/rocketlink-logo-32.png",
    "128": "images/rocketlink-logo-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{af79a474-bb48-41ed-a921-20f7356f5f6b}"
    }
  }
}