Examine source code of Librus Average

{
  "manifest_version": 2,
  "name": "__MSG_app_name__",
  "description": "__MSG_app_description__",
  "version": "2.8",
  "version_name": "2.8 firefox",
  "default_locale": "en",
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "64": "icons/icon64.png",
    "128": "icons/icon128.png"
  },
  "browser_action": {
    "default_popup": "html/options.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://synergia.librus.pl/przegladaj_oceny/uczen"
      ],
      "js": [
        "js/jquery-3.3.1.min.js",
        "js/support.js",
        "js/content_script.js"
      ]
    }
  ],
  "permissions": [
    "storage",
    "https://synergia.librus.pl/",
    "https://fonts.googleapis.com/"
  ],
  "content_security_policy": "script-src 'self'; object-src 'self'",
  "background": {
    "scripts": [
      "/js/support.js",
      "/js/background_analytics_manager.js"
    ],
    "persistent": false
  },
  "applications": {
    "gecko": {
      "id": "librus-average-roundel@zdul.xyz"
    }
  }
}