Examine source code of Custom New Tab

{
  "manifest_version": 3,
  "name": "Custom New Tab",
  "version": "1.0.0",
  "description": "Every new tab opens with the search bar already empty and focused — just start typing, nothing to select or delete. Displays the web page of your choice full-screen behind it.",
  "browser_specific_settings": {
    "gecko": {
      "id": "custom-new-tab@ataaki",
      "strict_min_version": "115.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "48": "icons/icon.svg",
    "96": "icons/icon.svg"
  },
  "permissions": [
    "storage"
  ],
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "chrome_url_overrides": {
    "newtab": "newtab.html"
  }
}