Examine source code of Undo Closed Tabs Button Pro

{
  "version": "0.2.2",
  "manifest_version": 2,
  "offline_enabled": true,
  "name": "Undo Closed Tabs Button",
  "homepage_url": "https://mybrowseraddon.com/undo.html",
  "description": "Easily undo closed tabs via your browser's toolbar popup!",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "options_page": "data/options/options.html",
  "permissions": [
    "tabs",
    "storage",
    "sessions"
  ],
  "browser_action": {
    "default_popup": "data/popup/popup.html",
    "default_title": "Undo Closed Tabs Button",
    "default_icon": {
      "16": "data/icons/toolbar/16.png",
      "32": "data/icons/toolbar/32.png",
      "48": "data/icons/toolbar/48.png",
      "64": "data/icons/toolbar/64.png"
    }
  },
  "icons": {
    "16": "data/icons/16.png",
    "32": "data/icons/32.png",
    "48": "data/icons/48.png",
    "64": "data/icons/64.png",
    "128": "data/icons/128.png"
  },
  "web_accessible_resources": [
    "data/popup/popup.html",
    "data/options/options.html",
    "data/icons/*.png"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{18faa553-ea2c-45a6-89cf-aa4bfe9b00d2}"
    }
  }
}