Examine source code of Audio Spatializer by 8Dfy

{
  "manifest_version": 3,
  "name": "Audio Spatializer by 8Dfy",
  "version": "1.4.0",
  "description": "Turn YouTube audio into immersive 8D spatial sound. Surround, HRTF 3D, binaural beats, video clips & export. Free, client-side.",
  "browser_specific_settings": {
    "gecko": {
      "id": "audio-spatializer@8dfy.xyz",
      "strict_min_version": "115.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": [
          "personallyIdentifyingInfo"
        ]
      }
    }
  },
  "permissions": [
    "storage",
    "activeTab",
    "scripting"
  ],
  "host_permissions": [
    "https://www.youtube.com/*",
    "https://music.youtube.com/*",
    "https://api.gumroad.com/*"
  ],
  "content_security_policy": {
    "extension_pages": "script-src 'self'; object-src 'self'"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.youtube.com/*",
        "https://music.youtube.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "ui/panel.css"
      ],
      "run_at": "document_start"
    }
  ],
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "web_accessible_resources": [
    {
      "resources": [
        "ui/*",
        "audio-engine.js",
        "worklet/spatial-processor.js"
      ],
      "matches": [
        "https://www.youtube.com/*",
        "https://music.youtube.com/*"
      ]
    }
  ]
}