Examine source code of IPCountry

{
  "manifest_version": 2,
  "name": "IPCountry",
  "version": "2.31",
  "description": "Check the country flags near IP addresses on any website!",
  "browser_specific_settings": {
    "gecko": {
      "id": "{fea0c929-b269-417d-9e7c-f7f434ce3742}",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      },
      "strict_min_version": "116.0"
    }
  },
  "permissions": [
    "<all_urls>"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "icons": {
    "64": "img/64.png",
    "128": "img/128.png"
  }
}