Examine source code of Universal Messenger

{
  "name": "Universal Messenger",
  "version": "0.0.5resigned1",
  "manifest_version": 2,
  "description": "Universal Messenger support many chat messenger services. You can chat with Skype, Facebook Messenger, Whatsapp, Yahoo, Hangouts, Telegram, etc... without install any application. Let's enjoy!",
  "homepage_url": "http://universalmessenger.com",
  "icons": {
    "16": "icons/chat16.png",
    "32": "icons/chat32.png",
    "64": "icons/chat64.png"
  },
  "default_locale": "en",
  "background": {
    "scripts": [
      "src/bg/background.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_icon": "icons/chat64.png",
    "default_title": "Open Universal Messenger",
    "default_popup": "src/browser_action/panel.html"
  },
  "permissions": [
    "cookies",
    "notifications",
    "tabs"
  ],
  "applications": {
    "gecko": {
      "id": "@com.virtualjame.universal-messenger",
      "strict_min_version": "48.0"
    }
  }
}