Examine source code of GimmeGimme

{
  "name": "GimmeGimme",
  "version": "1.3.1",
  "description": "GimmeGimme",
  "manifest_version": 2,
  "permissions": [
    "webNavigation",
    "tabs",
    "activeTab",
    "https://www.gimmegimme.nl/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icon16.png",
      "48": "icon48.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.gimmegimme.nl/*"
      ],
      "run_at": "document_end",
      "js": [
        "gimmegimme.js"
      ]
    }
  ],
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e3f5c5c2-443d-4aba-8a53-318bcbf3cd70}"
    }
  }
}