Examine source code of GNF to ISK

{
  "manifest_version": 3,
  "name": "GNF to ISK",
  "version": "1.0",
  "description": "Convert Guinean franc to Icelandic króna",
  "browser_specific_settings": {
    "gecko": {
      "id": "gnf-to-isk@example.com"
    }
  }
}