Examine source code of Multi Timer & Stopwatch

{
  "manifest_version": 2,
  "name": "Multi Timer & Stopwatch",
  "version": "1.0.0",
  "description": "Multiple countdown timers, stopwatch, lap tracking, and custom presets with notifications.",
  "permissions": [
    "storage",
    "notifications",
    "alarms"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon-16.png",
      "32": "icons/icon-32.png",
      "48": "icons/icon-48.png",
      "128": "icons/icon-128.png"
    }
  },
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{89c5b54b-8794-4afc-9cf5-ea197a946410}"
    }
  }
}