Examine source code of Stack Exchange Quick Downvote

{
  "manifest_version": 2,
  "homepage_url": "http://www.example.com",
  "developer": {
    "name": "wqin123",
    "url": "http://www.example.com"
  },
  "name": "Stack Exchange Downvoter Pro Tools",
  "short_name": "SE Auto DV",
  "author": "wqin123",
  "version": "4.2resigned1",
  "version_name": "4.1 Full Release",
  "default_locale": "en_GB",
  "description": "Stack Exchange Downvoter Pro Tools is a browser plug-in/extension/add-on for Chrome and Firefox that automatically serial-downvotes questions and answers on Stack Exchange communities/websites.",
  "applications": {
    "gecko": {
      "strict_min_version": "57.0",
      "id": "SE-AUTO-DOWNVOTE-APP@example.com"
    }
  },
  "icons": {
    "48": "icons/app-icon-48x48.png",
    "96": "icons/app-icon-48x48.png"
  },
  "permissions": [
    "storage",
    "activeTab",
    "background",
    "tabs",
    "*://*.stackexchange.com/*",
    "*://*.stackoverflow.com/*",
    "*://*.serverfault.com/*",
    "*://*.superuser.com/*",
    "*://*.mathoverflow.net/*",
    "*://*.askubuntu.com/*",
    "*://*.stackapps.com/*"
  ],
  "browser_action": {
    "default_icon": {
      "32": "icons/browser-toolbar-action-button-32x32.png"
    },
    "default_title": "Stack Exchange Downvoter Pro Tools"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "incognito": "spanning"
}