manifest.json

{
  "name": "Notification Changer for WhatsApp Web",
  "version": "1.0",
  "description": "A simple extension that allows the user to change the notification sound of web.whatsapp.com.",
  "permissions": [
    "activeTab", 
    "unlimitedStorage",
    "declarativeContent", 
    "storage", 
    "webRequest", 
    "webRequestBlocking",
    "*://web.whatsapp.com/*"
  ],
  "background": {
    "scripts": ["background.js"]
  },
  "page_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "images/icon_16.png",
      "32": "images/icon_32.png",
      "48": "images/icon_48.png",
      "128": "images/icon_128.png"
    }
  },
  "content_scripts": [{
    "js": ["content-script.js"],
    "matches": ["*://web.whatsapp.com/*"]
  }],
  "web_accessible_resources": [
    "modifier.js"
  ],
  "icons": {
    "16": "images/icon_16.png",
    "32": "images/icon_32.png",
    "48": "images/icon_48.png",
    "128": "images/icon_128.png"
  },
  "manifest_version": 2
}