Examine source code of Tab Pattern Closer

{
  "manifest_version": 3,
  "name": "Tab Pattern Closer",
  "version": "1.0.3",
  "description": "Close all tabs matching a URL or title pattern",
  "browser_specific_settings": {
    "gecko": {
      "id": "tab-pattern-closer@example.com"
    }
  },
  "permissions": [
    "tabs"
  ],
  "action": {
    "default_popup": "popup.html",
    "default_title": "Close tabs by pattern"
  },
  "icons": {
    "16": "icon-16.png",
    "48": "icon-48.png",
    "128": "icon-128.png"
  }
}