Examine source code of Hack the Form

{
  "name" : "Hack the Form",
  "description" : "A useful add-on for web developers to view hidden inputs in form.",
  "version" : "0.4",
  "manifest_version" : 2 ,
  "permissions" : [
    "activeTab" ,
    "storage" 
  ],
  "content_scripts" : [
    {
      "matches" : [
        "<all_urls>" 
      ],
      "js" : [
        "content.js" 
      ],
      "run_at" : "document_idle" 
    }
  ],
  "icons" : {
    "48" : "icons/icon-48.png",
    "96" : "icons/icon-96.png"
  },
  "background" : {
    "scripts" : [
      "main.js" 
    ],
    "persistent" : false 
  },
  "browser_action" : {
    "default_icon" : "icons/icon-96.png",
    "default_title" : "Hack the Form"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "form-hack-reloaded@7s26simon.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}