Examine source code of Auto Tab Closer Countdown

{
  "manifest_version": 3,
  "name": "Auto Tab Closer Countdown",
  "version": "1.0.0",
  "description": "Set a per-tab countdown timer and automatically close tabs when time is up.",
  "permissions": [
    "tabs",
    "storage",
    "alarms"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_title": "Tab Countdown Closer",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "auto-tab-closer-countdown@kbt.local",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  }
}