Add description to connect to headscale (#161)

Signed-off-by: Manuel Buil <[email protected]>

docs/installation/network-options.md

@@ -253,6 +253,8 @@ or provide that information in a file and use the parameter:
 --vpn-auth-file=$PATH_TO_FILE
 ```
 
+Optionally, if you have your own Tailscale server (e.g. headscale), you can connect to it by appending `,controlServerURL=$URL` to the vpn-auth parameters
+
 :::caution Warning
 
 If you plan on running several K3s clusters using the same tailscale network, please create appropriate [ACLs](https://tailscale.com/kb/1018/acls/) to avoid IP conflicts or use different podCIDR subnets for each cluster.