Examine source code of Group Extractor

{
  "version": "1.1.1",
  "manifest_version": 2,
  "name": "Group Extractor",
  "description": "Group Extractor is a tool that allows you to extract up to 3000 members from any Facebook™ group that you are a member of and save the data in a CSV file",
  "default_locale": "en",
  "icons": {
    "16": "icons/16.png",
    "48": "icons/48.png",
    "128": "icons/128.png"
  },
  "permissions": [
    "storage",
    "identity",
    "webRequest",
    "*://fbgroupextractor.extensionsbox.com/*",
    "*://*.facebook.com/*"
  ],
  "background": {
    "scripts": [
      "service-worker.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "19": "icons/19.png",
      "38": "icons/38.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.facebook.com/*"
      ],
      "js": [
        "contentScript.js"
      ],
      "css": [
        "style.css"
      ],
      "run_at": "document_end",
      "all_frames": false
    }
  ],
  "key": "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAn/8UIopRD61WFRT+peqShH18yAn6dvZ+nLvNnVkUvYvQEL/cjHf5eE9PwElS6w340BhI4yF47TXbr0hxVA2sbnXsrD7uz/musNtFzwd9XmA8bYnBa8iLDdrzlplnjI/UDjHau9vdrDJINlIi67d5M9LDFIbgAAvnV4iuGxdQwEUi5FO3G3DFZcOtrcEYcBf+umbPckAyrWEBB88bGhWFgzWS8XFu0GzQOYb6fwnIO842Wt0D/B7J3vxVLe7v6DSbxE5NZfWiY8kyZuqjfjoRPFZ6V9JP8PdTe+kuhT784PtWw+HGtYZ7cL68TuXtSA0MJUbLH8z0gOpEN2DxCMwpDwIDAQAB",
  "oauth2": {
    "client_id": "764556833347-p1g6pljtcbgk4vsqqtjs74bcumsiopji.apps.googleusercontent.com",
    "scopes": [
      "https://www.googleapis.com/auth/userinfo.email"
    ]
  },
  "content_security_policy": "script-src 'self' 'unsafe-eval'; object-src 'self'",
  "web_accessible_resources": [
    "assets/*",
    "libs/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{de353dce-ebf7-4f04-97bd-2ce5c42f2baf}"
    }
  }
}