Examine source code of DomainSentry

{
  "manifest_version": 3,
  "name": "DomainSentry",
  "version": "1.0",
  "description": "Domain Name Expiration Reminder and Management Tool",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "domainsentry@example.com"
    }
  },
  "permissions": [
    "storage",
    "alarms",
    "notifications"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_popup": "popup/popup.html",
    "default_icon": {
      "48": "icons/icon-48.png",
      "96": "icons/icon-96.png"
    }
  },
  "options_ui": {
    "page": "options/options.html",
    "open_in_tab": true
  }
}