Examine source code of Itunemachine Ringtones

{
  "manifest_version": 2,
  "name": "Itunemachine Ringtones",
  "description": "Find  high quality ringtones for your iPhone or Android phone ",
  "version": "1.0.0",
  "action": {
    "default_popup": "index.html",
    "default_icon": "assets/logo-large.png"
  },
  "icons": {
    "16": "assets/icon16.png",
    "32": "assets/icon32.png",
    "48": "assets/icon48.png",
    "128": "assets/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "hello@itunemachine.com"
    }
  }
}