Update documentation for nginx-gateway

Author: jb3

kubernetes/namespaces/nginx-gateway/README.md

@@ -19,6 +19,9 @@ We use NGINX Gateway Fabric to manage our ingress traffic. This replaced the pre
 
 NOTE: To upgrade/change values, switch from `helm install` to `helm upgrade`.
 
-## Creation of Gateway
+## Creation of Gateway & associated resources
 
 1. Apply `gateway.yaml` to create the Gateway resource that defines how ingress traffic should be routed to services in the cluster.
+2. Apply `reference-grants.yaml` to create ReferenceGrant resources that allow the Gateway to reference services in other namespaces.
+3. Apply snippets in `snippets/` to create reusable configuration snippets for use in HTTPRoute resources (notably mTLS enforcement).
+4. Finally, create routes from `routes/special/` and `routes/service-routes/` to define how traffic should be routed to services in the cluster.