Examine source code of Currency Converter

{
  "manifest_version": 2,
  "name": "Currency Converter",
  "version": "1.0",
  "description": "Addon for currency conversion",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icon.png"
    }
  },
  "permissions": [
    "activeTab",
    "https://api.exchangerate-api.com/v4/latest/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{1a9baf0f-3815-4104-8cf5-75f3201f16ed}"
    }
  }
}