Examine source code of CookieSweep

{
  "manifest_version": 2,
  "name": "CookieSweep",
  "version": "10",
  "description": "Automatically delete cookies for selected domains when their tab is closed",
  "browser_specific_settings": {
    "gecko": {
      "id": "{9f36fdea-f11c-465e-96f5-ad7f01bc1332}",
      "strict_min_version": "96.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "16": "img/icon-16.png",
    "32": "img/icon-32.png",
    "48": "img/icon-48.png",
    "96": "img/icon-96.png",
    "128": "img/icon-128.png"
  },
  "browser_action": {
    "default_popup": "ui/widget.html",
    "default_icon": {
      "16": "img/icon-16.png",
      "32": "img/icon-32.png",
      "48": "img/icon-48.png",
      "96": "img/icon-96.png",
      "128": "img/icon-128.png"
    }
  },
  "background": {
    "scripts": [
      "service/tracker.js"
    ]
  },
  "permissions": [
    "tabs",
    "storage",
    "cookies",
    "<all_urls>"
  ]
}