Examine source code of WA Sound +

{
  "manifest_version": 3,
  "name": "WA Sound +",
  "version": "1.2.0",
  "description": "Replace WhatsApp Web notification sound to a custom one or a random set of sounds",
  "icons": {
    "48": "icons/icon_48x48.png",
    "96": "icons/icon_96x96.png",
    "128": "icons/icon_128x128.png"
  },
  "action": {
    "default_title": "Custom sounds for WhatsApp Web"
  },
  "options_ui": {
    "page": "options/options.html",
    "open_in_tab": true
  },
  "host_permissions": [
    "https://web.whatsapp.com/*",
    "https://static.whatsapp.net/*"
  ],
  "permissions": [
    "storage",
    "declarativeNetRequest",
    "webRequest",
    "webRequestBlocking"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "service_worker": "background.js",
    "type": "module"
  },
  "web_accessible_resources": [
    {
      "resources": [
        "sounds/*"
      ],
      "matches": [
        "*://web.whatsapp.com/*",
        "*://static.whatsapp.net/*"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "WAS-plus@elfarostudios.net",
      "strict_min_version": "109.0"
    }
  }
}