Examine source code of Tab Cleaner

{
  "manifest_version": 2,
  "name": "Tab Cleaner",
  "description": "Close inactive tabs older than a threshold (minutes) and save them for recovery",
  "version": "1.0",
  "icons": {
    "64": "icons/icon64.png",
    "128": "icons/icon128.png"
  },
  "permissions": [
    "tabs",
    "storage",
    "alarms"
  ],
  "browser_action": {
    "default_icon": "icons/icon64.png",
    "default_title": "Tab Cleaner",
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{9afceb7b-e708-41ba-a361-4a5ccc028012}",
      "strict_min_version": "120.0"
    }
  }
}