Examine source code of CountDown

{
  "manifest_version": 3,
  "name": "CountDown",
  "version": "1.0.0",
  "description": "Simple countdown timer. Set minutes and seconds, start countdown with alerts.",
  "icons": {
    "48": "graphics/icon-48.png",
    "96": "graphics/icon-96.png",
    "128": "graphics/icon-128.png"
  },
  "action": {
    "default_icon": {
      "48": "graphics/icon-48.png",
      "96": "graphics/icon-96.png"
    },
    "default_title": "CountDown",
    "default_popup": "main-ui/timer.html"
  },
  "permissions": [
    "storage",
    "notifications"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "countdown@timer.alert",
      "strict_min_version": "109.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}