Examine source code of Audible Player Enhanced

{
  "manifest_version": 3,
  "name": "Audible Player Enhanced",
  "version": "0.3.17",
  "description": "Adds a dark theme and volume control to Audible's web player.",
  "icons": {
    "128": "assets/icon128.png"
  },
  "action": {
    "default_popup": "src/popup/popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "audible-player-enhanced@example.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "host_permissions": [
    "https://audible-player-enhanced.onrender.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://*.audible.com/*",
        "https://*.audible.co.uk/*",
        "https://*.audible.de/*",
        "https://*.audible.fr/*",
        "https://*.audible.co.jp/*",
        "https://*.audible.com.au/*",
        "https://*.audible.ca/*",
        "https://*.audible.in/*",
        "https://*.audible.it/*",
        "https://*.audible.es/*"
      ],
      "js": [
        "/content/content.js"
      ],
      "css": [
        "/assets/content.css"
      ]
    }
  ]
}