Examine source code of Smart Tab Cleaner

{
  "manifest_version": 2,
  "name": "Smart Tab Cleaner",
  "version": "1.0",
  "description": "Remind to clean old tabs if too many are open after a time period.",
  "permissions": [
    "tabs",
    "storage",
    "alarms"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{86e692b4-0924-4e0f-a82e-590716d35bb6}"
    }
  }
}