Examine source code of NestlyTab

{
  "name": "NestlyTab",
  "description": "Organize websites in a customizable column-based grid with drag-and-drop, tabs, and quick access.",
  "version": "1.2.3",
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "nestlytab@firefox.extension",
      "strict_min_version": "58.0"
    }
  },
  "chrome_url_overrides": {
    "newtab": "popup.html"
  },
  "permissions": [
    "storage",
    "contextMenus",
    "activeTab",
    "bookmarks",
    "tabs",
    "unlimitedStorage"
  ],
  "background": {
    "scripts": [
      "browser-polyfill-wrapper.js",
      "background.js"
    ],
    "persistent": true
  },
  "icons": {
    "16": "assets/icon-16.png",
    "48": "assets/icon-48.png",
    "128": "assets/icon-128.png"
  }
}