Examine source code of New containerized tab

{
  "manifest_version": 2,
  "name": "New containerized tab",
  "version": "1.0",
  "description": "Open a new tab in the same container as the current tab using keyboard shortcuts",
  "permissions": [
    "tabs",
    "cookies"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "commands": {
    "open-containerized-tab": {
      "suggested_key": {
        "default": "Ctrl+Alt+E",
        "mac": "Command+Shift+E"
      },
      "description": "Open new tab in current container"
    }
  },
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "browser_action": {
    "default_icon": {
      "16": "icons/icon-16.png",
      "32": "icons/icon-32.png"
    },
    "default_title": "New containerized tab"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e9b02e63-da4d-482c-a0f6-28477c846d47}"
    }
  }
}