Examine source code of KoalaSync

{
  "manifest_version": 3,
  "default_locale": "en",
  "name": "KoalaSync",
  "version": "2.4.3",
  "description": "Synchronize video playback on YouTube, Netflix, Emby, Jellyfin, and any HTML5 site in real-time with friends.",
  "permissions": [
    "storage",
    "tabs",
    "scripting",
    "alarms",
    "activeTab",
    "notifications"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png",
      "48": "icons/icon48.png",
      "96": "icons/icon96.png",
      "128": "icons/icon128.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "https://sync.koalastuff.net/*"
      ],
      "js": [
        "bridge.js"
      ],
      "run_at": "document_start"
    }
  ],
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "96": "icons/icon96.png",
    "128": "icons/icon128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "type": "module"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "koalasync@koalastuff.net",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}