Examine source code of TabOnce

{
  "manifest_version": 3,
  "name": "TabOnce",
  "description": "Focus an existing matching tab instead of opening a duplicate.",
  "version": "1.2.0",
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png"
  },
  "permissions": [
    "scripting",
    "storage",
    "tabs"
  ],
  "optional_host_permissions": [
    "http://*/*",
    "https://*/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_page": "options.html",
  "action": {
    "default_title": "TabOnce rules",
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon-16.png",
      "32": "icons/icon-32.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "tab-once@dkarter.dev",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}