Examine source code of Length Unit Converter

{
  "manifest_version": 3,
  "name": "Length Unit Converter",
  "version": "1.0",
  "description": "Convert feet to meters and vice versa.",
  "permissions": [
    "activeTab"
  ],
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/ico8n16.png",
      "48": "icons/icon48.png",
      "128": "icons/icon12.png"
    }
  },
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "umergumn1@gmail.com"
    }
  }
}