Examine source code of Pageify

{
  "manifest_version": 2,
  "name": "Pageify",
  "description": "Pageify extension",
  "version": "1.0.0",
  "browser_action": {
    "default_popup": "setkey.html"
  },
  "applications": {
    "gecko": {
      "id": "pageify@pageify.be"
    }
  },
  "permissions": [
    "activeTab",
    "tabs",
    "storage"
  ]
}