Subnetmask Calculator

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 3,
  "name": "Subnetmask Calculator",
  "description": "A simple subnetmask calculator",
  "version": "2.0",
  "permissions": [],
  "action": {
    "default_popup": "index.html",
    "default_icon": {
      "16": "icon.png",
      "48": "icon.png",
      "128": "icon.png"
    }
  },
  "icons": {
    "16": "icon.png",
    "48": "icon.png",
    "128": "icon.png"
  }
}