Examine source code of osu! preview

{
  "manifest_version": 3,
  "name": "osu! preview",
  "version": "1.2.1",
  "description": "Preview osu! beatmaps inside the browser",
  "permissions": [
    "storage",
    "tabs",
    "declarativeNetRequest",
    "unlimitedStorage",
    "downloads"
  ],
  "host_permissions": [
    "https://*.ppy.sh/*"
  ],
  "background": {
    "scripts": [
      "/src/background.js"
    ],
    "type": "module"
  },
  "action": {
    "default_title": "osu! preview",
    "default_popup": "/src/popup.html"
  },
  "icons": {
    "16": "/assets/icon16.png",
    "48": "/assets/icon48.png",
    "128": "/assets/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "osupreview@technozamb.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}