NGF: Update gateway addresses compatibility document with IP family comment (nginx#1126)

Add a small comment on IP families to gateway addresses compatibility document.

Author: bjee19

content/ngf/overview/gateway-api-compatibility.md

@@ -101,7 +101,7 @@ See the [controller]({{< ref "/ngf/reference/cli-help.md#controller">}}) command
       - `certificateRefs` - The TLS certificate and key must be stored in a Secret resource of type `kubernetes.io/tls`. Only a single reference is supported.
       - `options`: Not supported.
     - `allowedRoutes`: Supported.
-  - `addresses`: Valid IPAddresses will be added to the `externalIP` field in the related Services fronting NGINX.
+  - `addresses`: Valid IPAddresses will be added to the `externalIP` field in the related Services fronting NGINX. Users should ensure that the IP Family of the address matches the IP Family set in the NginxProxy resource (default is dual, meaning both IPv4 and IPv6), otherwise there may be networking issues.
       - `type`: Partially supported. Allowed value: `IPAddress`.
       - `value`: Partially supported. Dynamic address allocation when value is unspecified is not supported.
   - `backendTLS`: Not supported.