Examine source code of Duplicate Tab

{
  "manifest_version": 2,
  "name": "Duplicate Tab",
  "version": "1.0",
  "description": "Duplicate Tab for Firefox mobile",
  "permissions": [
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_icon": {
      "16": "icons/icon-16.png",
      "48": "icons/icon-48.png",
      "128": "icons/icon-128.png"
    },
    "default_title": "Duplicate Tab"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{48297ba2-6f12-4a66-82ab-b3227cc63fc8}"
    }
  }
}