Examine source code of Tab manager

{
  "browser_action": {
    "browser_style": true,
    "default_title": "Tab manager",
    "default_popup": "tabmgr.html",
    "default_icon": {
      "64": "tabmgr.png"
    }
  },
  "applications": {
    "gecko": {
      "id": "tab-manager@chocobeton"
    }
  },
  "description": "Allows basic operations on open tabs, such as copying the URLs to the clipboard, and saving the tab list to a file.",
  "manifest_version": 2,
  "author": "Ale",
  "name": "Tab manager",
  "permissions": [
    "tabs",
    "clipboardWrite",
    "downloads",
    "storage"
  ],
  "icons": {
    "64": "tabmgr.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "pref.html"
  },
  "version": "0.22resigned1"
}