Examine source code of Kitchen Timers

{
  "manifest_version": 2,
  "name": "Kitchen Timers",
  "description": "A rack of independent countdowns for cooking, laundry or anything else with a few things on the go. Name each one, reuse the presets, and get a notification when each finishes.",
  "version": "3.1.5.6",
  "browser_specific_settings": {
    "gecko": {
      "id": "{37d3976f-2ece-4a3d-b2ce-7d94c39829d8}",
      "strict_min_version": "101.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "32": "assets/icon-32.png",
    "48": "assets/icon-48.png",
    "64": "assets/icon-64.png",
    "96": "assets/icon-96.png",
    "128": "assets/icon-128.png"
  },
  "browser_action": {
    "default_title": "Kitchen Timers",
    "default_popup": "popup.html",
    "default_icon": {
      "32": "assets/icon-32.png",
      "48": "assets/icon-48.png",
      "64": "assets/icon-64.png"
    }
  },
  "permissions": [
    "storage",
    "notifications",
    "alarms"
  ],
  "background": {
    "scripts": [
      "core/core.js",
      "core/background.js"
    ],
    "persistent": true
  }
}