Examine source code of Simply One Tab

{
  "name": "Simply One Tab",
  "id": "simplyonetab",
  "description": "Closes and lists your recent tabs is one page",
  "version": "1.0.2",
  "manifest_version": 3,
  "permissions": [
    "storage",
    "tabs",
    "scripting"
  ],
  "action": {
    "default_title": "Click me to join all tabs in a one-tab list",
    "default_icon": "simplyonetab.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{0d11e7b9-fc58-40d0-b220-5f08d22e2481}"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}