Examine source code of Smart Tab Close

{
  "manifest_version": 3,
  "name": "Smart Tab Close",
  "version": "1.0.0",
  "description": "Switches to the previously active tab when a tab is closed.",
  "permissions": [
    "storage",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "16": "icon16.png",
    "32": "icon32.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "smart-tab-close@shakie",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      },
      "strict_min_version": "128.0"
    }
  }
}