Examine source code of Auto Close Duplicate Tabs

{
  "manifest_version": 2,
  "name": "Auto Close Duplicate Tabs",
  "version": "1.0",
  "description": "Finds duplicate tabs and closes extras (keeps one tab per URL).",
  "permissions": [
    "tabs"
  ],
  "browser_action": {
    "default_title": "Close Duplicate Tabs",
    "default_icon": {
      "64": "icon64.png",
      "128": "icon128.png"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "64": "icon64.png",
    "128": "icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{4cc0b2e0-035d-40f5-84bd-23b7579feaee}",
      "strict_min_version": "125.0"
    }
  }
}