Examine source code of Browser Window Closer

{
  "manifest_version": 2,
  "name": "Browser Window Closer",
  "short_name": "Browser Window Closer",
  "version": "1.1resigned1",
  "description": "Close all open Window & tabs except active tab on single click",
  "icons": {
    "16": "images/Icon-16.png",
    "48": "images/Icon-48.png",
    "128": "images/Icon-128.png"
  },
  "permissions": [
    "tabs"
  ],
  "browser_action": {
    "default_icon": {
      "19": "images/Icon-19.png",
      "38": "images/Icon-38.png"
    },
    "default_title": "Browser Window Closer"
  },
  "background": {
    "scripts": [
      "js/background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{deea35db-afed-43cd-9e2b-1a92dd56b79e}"
    }
  }
}