Examine source code of Retrofy Page

{
  "manifest_version": 3,
  "name": "Retrofy Page",
  "description": "Turn ordinary webpages into a tasteful 1990s-style version on demand.",
  "version": "0.3.0",
  "action": {
    "default_icon": {
      "16": "assets/icon16.png",
      "48": "assets/icon48.png",
      "128": "assets/icon128.png"
    },
    "default_popup": "popup.html",
    "default_title": "Retrofy Page"
  },
  "icons": {
    "16": "assets/icon16.png",
    "48": "assets/icon48.png",
    "128": "assets/icon128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "activeTab",
    "scripting",
    "storage",
    "webNavigation"
  ],
  "host_permissions": [],
  "web_accessible_resources": [
    {
      "resources": [
        "assets/dialup.wav",
        "assets/win95ish-chime.wav"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "retrofy-page@valentinoricco",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}