Examine source code of YouTube Default Speed

{
  "manifest_version": 2,
  "name": "YouTube Default Speed",
  "version": "1.5.2",
  "description": "Automatically adjust YouTube video playback speed with smart music detection",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "permissions": [
    "storage",
    "*://*.youtube.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "content-script.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "browser_specific_settings": {
    "gecko": {
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      },
      "id": "{303828fb-5eed-4bd9-8c63-4548bf9c9665}"
    }
  }
}