Examine source code of 17Track This

{
  "background": {
    "scripts": [
      "menu.js"
    ]
  },
  "description": "Adds a context menu for searching tracking numbers on 17Track website",
  "icons": {
    "16": "icon.png"
  },
  "manifest_version": 2,
  "name": "17Track This",
  "permissions": [
    "contextMenus"
  ],
  "version": "2.1resigned1",
  "homepage_url": "http://www.inframe.ro",
  "browser_specific_settings": {
    "gecko": {
      "id": "{b22139e9-867c-4416-b8fd-f52f392c4b47}"
    }
  }
}