Examine source code of To icon size

{
  "manifest_version": 3,
  "name": "To icon size",
  "version": "1.0",
  "description": "Upload an image and generate icons in various sizes.",
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "images/icon16.png",
      "48": "images/icon48.png",
      "128": "images/icon128.png"
    }
  },
  "background": {
    "service_worker": "background.js",
    "scripts": [
      "background.js"
    ],
    "type": "module"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "toiconsize@correia.extensions",
      "strict_min_version": "128.0"
    }
  },
  "permissions": [
    "downloads",
    "storage"
  ]
}