Examine source code of Event Countdown

{
  "manifest_version": 3,
  "name": "Event Countdown",
  "version": "1.3",
  "browser_specific_settings": {
    "gecko": {
      "id": "{5469956b-801b-4171-8728-662580577717}",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "description": "A simple countdown timer for your upcoming events.",
  "permissions": [
    "storage"
  ],
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icons/icon-48.png"
    }
  },
  "chrome_url_overrides": {
    "newtab": "newtab.html"
  },
  "chrome_settings_overrides": {
    "homepage": "newtab.html"
  },
  "icons": {
    "48": "icons/icon-48.png"
  }
}