Examine source code of Tab Parent Focus

{
  "manifest_version": 2,
  "name": "Tab Parent Focus",
  "version": "1.0.0",
  "description": "Returns focus to the parent tab when an active child tab is closed.",
  "permissions": [
    "tabs",
    "storage",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_title": "Tab Parent Focus",
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icons/icon.svg",
      "96": "icons/icon.svg"
    }
  },
  "sidebar_action": {
    "default_title": "Tab Tree",
    "default_panel": "sidebar/sidebar.html",
    "default_icon": {
      "48": "icons/icon.svg",
      "96": "icons/icon.svg"
    },
    "open_at_install": false
  },
  "icons": {
    "48": "icons/icon.svg",
    "96": "icons/icon.svg"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "tab-parent-focus@example.local",
      "strict_min_version": "115.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}