Examine source code of LibrusPro

{
  "name": "LibrusPro - rozszerzenie do Librusa",
  "version": "3.4.0",
  "description": "Ulepsz Librusa już dziś! Może marzysz o ciemnym motywie, liczeniu średnich i procentów frekwencji oraz własnym terminarzu?",
  "manifest_version": 2,
  "author": "Maks Kowalski",
  "short_name": "LibrusPro",
  "permissions": [
    "storage",
    "https://synergia.librus.pl/*",
    "https://portal.librus.pl/*"
  ],
  "icons": {
    "512": "img/icon.png"
  },
  "browser_action": {
    "default_icon": "img/icon.png",
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "https://synergia.librus.pl/*"
      ],
      "js": [
        "librusPro.js"
      ],
      "all_frames": true
    },
    {
      "matches": [
        "https://synergia.librus.pl/*"
      ],
      "css": [
        "librusPro.css"
      ],
      "run_at": "document_start"
    },
    {
      "matches": [
        "https://portal.librus.pl/*"
      ],
      "js": [
        "portal.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "img/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{2ddaa55f-7db8-460a-bf9b-01396684935b}"
    }
  }
}