Examine source code of URL Shortener Addon

{
  "name": "URL Shortener Addon",
  "description": "URL Shortener Extension Addon. Quick & Easy - Stable & Security - Support 24/7",
  "version": "3.6.3",
  "manifest_version": 2,
  "permissions": [
    "activeTab",
    "https://shortbe.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "http://shortbe.com/*",
        "https://shortbe.com/*"
      ],
      "js": [
        "includes/js/background.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": "/images/icon.png",
    "default_popup": "index.html"
  },
  "icons": {
    "16": "/images/icon.png",
    "48": "/images/icon-128.png",
    "128": "/images/icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{3b8db1f5-64b2-4755-b902-aac5e1043c8a}"
    }
  }
}