Examine source code of Duolingo Language

{
  "manifest_version": 2,
  "name": "Duolingo Language Learning Extension",
  "version": "1.0.0",
  "description": "Small tools to help language learners on Duolingo: quick translations, dark mode toggle, and word frequency panel.",
  "icons": {
    "48": "icons/icon48.png",
    "96": "icons/icon96.png"
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Duolingo Tools",
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icons/icon48.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.duolingo.com/*"
      ],
      "js": [
        "content_script.js"
      ],
      "run_at": "document_end"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{c9a2f5d8-6071-4b52-bb4e-ca77d74a9a9a}"
    }
  }
}