Examine source code of AboutConfig Toggler

{
  "manifest_version": 2,
  "name": "AboutConfig Toggler",
  "version": "1.0",
  "description": "Toggle about:config preferences",
  "permissions": [
    "aboutConfig",
    "http://localhost:3000/*"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Toggle"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{6902bfea-369a-49fd-8ae8-cd081903dc79}"
    }
  }
}