Examine source code of Count Duplicate Tabs

{
  "author": "igorlogius",
  "homepage_url": "https://github.com/igorlogius/count-duplicate-tabs",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_area": "navbar"
  },
  "icons": {
    "128": "icon.png"
  },
  "manifest_version": 2,
  "name": "Count Duplicate Tabs",
  "description": "Shows the total amount of duplicate tabs and allows to close them - Same URLs in different containers are not treated as duplicates",
  "permissions": [
    "cookies",
    "tabs"
  ],
  "version": "1.0.1",
  "browser_specific_settings": {
    "gecko": {
      "id": "{61e1cdac-d439-48ee-9aa8-344217431f0a}"
    }
  }
}