Examine source code of VisaSentinel

{
  "manifest_version": 3,
  "name": "VisaSentinel",
  "version": "1.5.0",
  "description": "Monitors US visa OFC appointment slots and alerts you via Telegram when slots become available.",
  "icons": {
    "16": "icon16.png",
    "32": "icon32.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "permissions": [
    "storage",
    "alarms",
    "tabs",
    "scripting",
    "downloads",
    "activeTab",
    "webRequest",
    "notifications"
  ],
  "host_permissions": [
    "https://www.usvisascheduling.com/*",
    "https://api.telegram.org/*",
    "https://atlasauth.b2clogin.com/*",
    "https://visasentinel.online/*",
    "https://payhip.com/*",
    "https://hc-ping.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://www.usvisascheduling.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_popup": "popup.html",
    "default_title": "VisaSentinel",
    "default_icon": {
      "16": "icon16.png",
      "32": "icon32.png",
      "48": "icon48.png",
      "128": "icon128.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "visasentinel@yourdomain.com",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "websiteContent"
        ]
      }
    }
  }
}