Examine source code of Shortcutter

{
  "manifest_version": 2,
  "name": "Shortcutter",
  "version": "1.0",
  "description": "A Firefox extension to create custom shortcuts for website URLs",
  "icons": {
    "16": "icons/131.png",
    "48": "icons/156.png",
    "64": "icons/172.png"
  },
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "contentScript.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": "icons/156.png",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{53b4ea2d-0d07-4f48-8f18-2804c747eb94}"
    }
  }
}