Examine source code of Utopic Radio

{
  "applications": {
    "gecko": {
      "id": "firefox-app@utopicradio.com"
    }
  },
  "name": "Utopic Radio",
  "description": "Utopic Radio - Bonne humeur garantie !",
  "version": "1.4resigned1",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "19": "19.png",
      "38": "38.png",
      "128": "128.png",
      "256": "256.png"
    }
  },
  "homepage_url": "https://utopicradio.com/",
  "icons": {
    "16": "16.png",
    "48": "48.png",
    "128": "128.png",
    "256": "256.png"
  },
  "permissions": [
    "contextMenus",
    "tabs",
    "http://*/*",
    "https://*/*"
  ],
  "manifest_version": 2
}