Examine source code of What week is it

{
  "name": "What week is it",
  "description": "Quickly find the current week we're in! You'll never have to ask anyone what week it is ever again.",
  "version": "0.0.0.1",
  "manifest_version": 3,
  "action": {
    "default_popup": "index.html"
  },
  "icons": {
    "16": "images/icon_16.png",
    "32": "images/icon_32.png",
    "48": "images/icon_48.png",
    "128": "images/icon_128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ed3e519e-4ab7-4fc3-8d19-49bf6e3d08c0}"
    }
  }
}