Examine source code of New Tab Page Container

{
  "manifest_version": 2,
  "name": "New tab containers",
  "version": "4.1.0",
  "description": "Show contextual identities on new tab page",
  "homepage_url": "https://github.com/KazuAlex/firefox-new-tab-page-container",
  "browser_action": {
    "default_title": "Containers page",
    "default_icon": "/assets/icons/new-tab.svg",
    "theme_icons": [
      {
        "light": "/assets/icons/new-tab-light.svg",
        "dark": "/assets/icons/new-tab.svg",
        "size": 16
      },
      {
        "light": "/assets/icons/new-tab-light.svg",
        "dark": "/assets/icons/new-tab.svg",
        "size": 32
      },
      {
        "light": "/assets/icons/new-tab-light.svg",
        "dark": "/assets/icons/new-tab.svg",
        "size": 64
      },
      {
        "light": "/assets/icons/new-tab-light.svg",
        "dark": "/assets/icons/new-tab.svg",
        "size": 96
      },
      {
        "light": "/assets/icons/new-tab-light.svg",
        "dark": "/assets/icons/new-tab.svg",
        "size": 128
      }
    ]
  },
  "icons": {
    "48": "/assets/icons/new-tab.svg",
    "96": "/assets/icons/new-tab.svg"
  },
  "permissions": [
    "contextualIdentities",
    "cookies",
    "tabs",
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "strict_min_version": "64.0",
      "id": "{1a6610a7-0042-4990-b969-a3b9ac778b49}"
    }
  },
  "chrome_url_overrides": {
    "newtab": "index.html"
  }
}