doc(smartcards): fix incomplete sentence. Fix #834

Author: bastienwirtz

docs/customservices.md

@@ -49,7 +49,11 @@ within Homer:
 - [What's Up Docker](#whats-up-docker)
 
 > [!IMPORTANT]  
-> Using smart cards will probably requires
+> Using smart cards, which interact with other services, will require either that:
+>
+> - All services are exposed on the **same domain** as homer (mydomain,tld/pihole, mydomain,tld/proxmox), avoiding any cross domain request issues (CORS).
+> - All services **accecpt cross site requests** (= send the necessary CORS headers, either set directly in the service configuration if possible, or using a proxy to set the headers)
+>
 > If you experiencing any issue, please have a look to the [troubleshooting](troubleshooting.md#my-service-card-doesnt-work-nothing-appears-or-offline-status-is-displayed-pi-hole-sonarr-ping-) page.
 
 ## Common options