Examine source code of CloseAfter

{
  "manifest_version": 2,
  "name": "CloseAfter",
  "version": "3.3",
  "description": "Close any tab automatically after a set amount of time",
  "browser_specific_settings": {
    "gecko": {
      "id": "{e406bbf4-29d6-4657-b50e-d3e06d89b59c}",
      "strict_min_version": "96.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "16": "assets/icon16.png",
    "32": "assets/icon32.png",
    "48": "assets/icon48.png",
    "96": "assets/icon96.png",
    "128": "assets/icon128.png"
  },
  "browser_action": {
    "default_popup": "ui/popup.html",
    "default_icon": {
      "16": "assets/icon16.png",
      "32": "assets/icon32.png",
      "48": "assets/icon48.png",
      "96": "assets/icon96.png",
      "128": "assets/icon128.png"
    }
  },
  "background": {
    "scripts": [
      "bg/background.js"
    ]
  },
  "permissions": [
    "tabs",
    "storage",
    "alarms"
  ]
}