Examine source code of URL unescape

{
  "manifest_version": 2,
  "name": "URL unescape",
  "version": "0.9",
  "author": "Saumon",
  "default_locale": "en",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "menus"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{279c9334-bff4-4f4c-a069-76aeb472017c}"
    }
  }
}