Examine source code of SubNet Calc

{
  "name": "SubNet Calc",
  "version": "1.0",
  "description": "A Firefox sidebar add-on for calculating IPv4 subnets. Computes network addresses, broadcast addresses, host ranges, and usable hosts using ipaddr.js.",
  "permissions": [],
  "sidebar_action": {
    "default_title": "SubNet Calc",
    "default_panel": "sidebar.html"
  },
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "{e22232a0-417a-4092-b4c7-4b9bc36259da}"
    }
  }
}