Examine source code of Currency Converter

{
  "manifest_version": 2,
  "name": "Currency Converter",
  "version": "1.0",
  "description": "Addon to convert currency values ​​quickly.",
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "permissions": [
    "https://api.currencyapi.com/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{23054424-9cf6-4c7c-b512-12090be36128}"
    }
  }
}