dev-guide: add k-nmstate metrics port

Author: mkowalski

dev-guide/host-port-registry.md

@@ -78,6 +78,7 @@ Ports are assumed to be used on all nodes in all clusters unless otherwise speci
 | 6385      | ironic                                          |          | yes                | metal         | 4.4   | baremetal provisioning                                                                                           |
 | 6388      | ironic (internal)                               |          | yes                | metal         | 4.12  | baremetal provisioning                                                                                           |
 | 6443      | kube-apiserver                                  |          | yes                | apiserver     |       |                                                                                                                  |
+| 8089      | kubernetes-nmstate                              |          | no                 | opnet         |       | metrics                                                                                                          |
 | 9001      | machine-config-daemon oauth proxy               |          |                    | node          |       | metrics                                                                                                          |
 | 9099      | cluster-version operator                        | HTTPS    | yes                | updates       |       | metrics                                                                                                          |
 | 9100      | node-exporter                                   |          | no                 | monitoring    |       | metrics                                                                                                          |