Examine source code of Daily English Word

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 3,
  "name": "Daily English Word",
  "description": "Show a new English word each day in a simple and minimal popup.",
  "version": "1.0.0",
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "128": "icon128.png"
    }
  }
}