chore: Added kubernetes example file

[SeeMyPing]

Description

This PR adds a comprehensive example manifest for deploying RustDesk Server on Kubernetes. This template provides a starting point for users wishing to host their own RustDesk infrastructure using cloud-native patterns.

Changes

• Created kubernetes/example.yaml which includes:
  • Deployment: A dual-container pod setup running both hbbs (ID Server) and hbbr (Relay Server) side-by-side.
  • Service: exposing all necessary ports (21115-21119) for TCP/UDP traffic.
  • PersistentVolumeClaim: A 1Gi PVC claim to ensure persistent storage for server keys and database.
• Implemented RELAY_HOST environment variable substitution in the hbbs command to facilitate easier configuration of the relay address.

Usage

Users can deploy this example by customizing the RELAY_HOST value and applying the manifest:

kubectl apply -f https://raw.githubusercontent.com/rustdesk/rustdesk-server/refs/heads/master/kubernetes/example.yaml

Checklist

• Manifest validates against Kubernetes schemas
• Environment variables are correctly propagated
• Service ports match RustDesk documentation