Examine source code of World Clock Toolbar

{
  "manifest_version": 2,
  "name": "World Clock Toolbar",
  "version": "1.0",
  "description": "Show 2–3 city clocks in the toolbar popup. Configure cities and formats.",
  "icons": {
    "48": "icons/icon48.svg",
    "128": "icons/icon128.svg"
  },
  "browser_action": {
    "default_title": "World Clock",
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icons/icon48.svg"
    }
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{b32b9720-37e6-4809-9526-ca126f6f4d6c}"
    }
  }
}