Examine source code of Duplicate Tabs Closer

{
  "manifest_version": 2,
  "name": "Duplicate Tabs Closer",
  "version": "3.6.1",
  "author": "Peuj",
  "default_locale": "en",
  "description": "Duplicate Tabs Closer",
  "icons": {
    "48": "images/auto_close_32.png"
  },
  "applications": {
    "gecko": {
      "id": "8eb46bae-a28b-4271-b139-53f788c41625@jetpack",
      "strict_min_version": "68.0"
    }
  },
  "background": {
    "scripts": [
      "helper.js",
      "tabsInfo.js",
      "options.js",
      "urlUtils.js",
      "badge.js",
      "worker.js",
      "messageListener.js",
      "background.js"
    ]
  },
  "browser_action": {
    "browser_style": false,
    "default_icon": {
      "16": "images/auto_close_16.png",
      "32": "images/auto_close_32.png"
    },
    "default_title": "Duplicate Tabs Closer",
    "default_popup": "popup/popup.html"
  },
  "permissions": [
    "cookies",
    "tabs",
    "webNavigation",
    "storage",
    "contextualIdentities"
  ],
  "commands": {
    "close-duplicate-tabs": {
      "suggested_key": {
        "default": "Alt+Shift+W"
      },
      "description": "Close all duplicate tabs"
    },
    "toggle-close-automatically": {
      "suggested_key": {
        "default": "Alt+Shift+D"
      },
      "description": "Toggle close automatically"
    }
  },
  "options_ui": {
    "page": "optionPage/optionPage.html",
    "browser_style": false,
    "open_in_tab": true
  }
}