Examine source code of Daily Time Machine

{
  "manifest_version": 2,
  "name": "Daily Time Machine",
  "description": "Travel through the calendar: milestones of history for every date, plus a curious fact when the archive is quiet.",
  "version": "3.2.0.2",
  "browser_specific_settings": {
    "gecko": {
      "id": "{3ed3146f-8474-4293-b06f-8ac8fdd8d97a}",
      "strict_min_version": "101.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "32": "images/icon-32.png",
    "48": "images/icon-48.png",
    "64": "images/icon-64.png",
    "96": "images/icon-96.png",
    "128": "images/icon-128.png"
  },
  "browser_action": {
    "default_title": "Daily Time Machine",
    "default_popup": "scripts/popup.html",
    "default_icon": {
      "32": "images/icon-32.png",
      "48": "images/icon-48.png",
      "64": "images/icon-64.png",
      "96": "images/icon-96.png",
      "128": "images/icon-128.png"
    }
  }
}