Examine source code of Stopwatch Timer Countdown

{
  "manifest_version": 2,
  "name": "Stopwatch Timer Countdown",
  "version": "1.0.0",
  "description": "Stopwatch, countdown timer and lap tracker with alarm notifications",
  "permissions": [
    "storage",
    "notifications"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "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": "c2e5ce698d17f62dc1efea5f3fed869e9c517b5e@extension.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}