Examine source code of World Clocks

{
  "manifest_version": 3,
  "name": "World Clocks",
  "version": "1.1.2",
  "description": "Replace your new tab page with world clocks",
  "permissions": [
    "storage"
  ],
  "chrome_url_overrides": {
    "newtab": "newtab.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "world-clocks@nosammai"
    }
  },
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  }
}