docs: update .env.example with comments and GRAPH_API_VERSION

Added WhatsApp Cloud API credentials and webhook setup information.

Author: ibrahimpelumi6142

.env.example

@@ -1,4 +1,12 @@
+# WhatsApp Cloud API Credentials
+# Get these from https://developers.facebook.com/apps/
 WHATSAPP_TOKEN=your_api_token_here
 WHATSAPP_PHONE_NUMBER_ID=your_phone_number_id
 WHATSAPP_SECRET=your_app_secret
+
+# Webhook Verification
+# Choose any secure random string for webhook setup
 VERIFY_TOKEN=your_webhook_verify_token
+
+# Graph API Version (optional, defaults to v21.0)
+GRAPH_API_VERSION=v21.0