Examine source code of Domain Extractor

{
  "manifest_version": 2,
  "name": "Domain Extractor",
  "version": "1.1",
  "description": "Extract the domain of the current tab with a shortcut key.",
  "permissions": [
    "tabs",
    "clipboardWrite"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "commands": {
    "extract_domain": {
      "suggested_key": {
        "default": "Alt+Ctrl+D"
      },
      "description": "Extract the domain of the current tab"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c5d0b5cc-4334-4532-ba25-d4a9412a82ff}"
    }
  }
}