Add note on setting hosts for Varnish configuration

Added important note about configuring Varnish in Shopware to prevent cURL SSL ERRORS.

Author: TimVNL

docs/ecommerce-applications/shopware-6/how-to-configure-varnish-for-shopware-6.md

@@ -88,6 +88,9 @@ location ~ \.php$ {
 
 Go to [Shopware's Reverse Http Cache documentation](https://developer.shopware.com/docs/guides/hosting/infrastructure/reverse-http-cache) to configure Shopware to take Varnish into account.
 
+```{important}
+Make sure your hosts in the shopware =>  http_cache => reverse_proxy section is set to `http://varnish:8081` to prevent cURL SSL ERRORS.
+```
 ## Step Four: Implement a .vcl Into Varnish
 
 To actually use Varnish you need to implement a varnish config file, a .vcl. If you're on Shopware >= 6.4, fetch the [Varnish configuration from their documentation](https://developer.shopware.com/docs/guides/hosting/infrastructure/reverse-http-cache#configure-varnish) (copy the code block starting with *vcl 4.0;*). Or you can create your own.