Examine source code of Container New Tab

{
  "browser_specific_settings": {
    "gecko": {
      "id": "@containernewtab",
      "strict_min_version": "57.0"
    }
  },
  "manifest_version": 2,
  "name": "__MSG_name__",
  "version": "2.1",
  "description": "__MSG_description__",
  "default_locale": "en",
  "chrome_url_overrides": {
    "newtab": "ext/redirect.html"
  },
  "icons": {
    "48": "ext/icon.svg",
    "128": "ext/icon.svg"
  },
  "background": {
    "scripts": [
      "ext/background.js"
    ],
    "persistent": false
  },
  "options_ui": {
    "page": "ext/options.html",
    "open_in_tab": true,
    "browser_style": false
  },
  "permissions": [
    "contextualIdentities",
    "cookies",
    "storage"
  ],
  "browser_action": {
    "browser_style": true,
    "default_icon": "ext/icon.svg",
    "default_title": "__MSG_prefsPage__"
  },
  "commands": {
    "_execute_browser_action": {
      "description": "__MSG_prefsPage__"
    }
  }
}