Examine source code of Calculator

{
  "manifest_version": 3,
  "name": "Calculator",
  "version": "1.0",
  "description": "A simple calculator extension.",
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "calculator-addon@example.com"
    }
  },
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icon.png"
    }
  }
}