Examine source code of Prem's Stopwatch

{
  "manifest_version": 3,
  "name": "Stopwatch Extension",
  "version": "1.0",
  "description": "A simple stopwatch that opens in a new tab.",
  "permissions": [
    "tabs"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "background": {
    "service_worker": "background.js",
    "scripts": [
      "background.js"
    ]
  },
  "commands": {
    "open-stopwatch": {
      "suggested_key": {
        "default": "Ctrl+Shift+L"
      },
      "description": "Open the stopwatch in a new tab"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "stopwatch@example.com"
    }
  }
}