Rename and add content to network fabric article

Author: jmmason70

articles/operator-nexus/concepts-network-fabric-optionA-optionB.md renamed to articles/operator-nexus/concepts-network-fabric-optiona-optionb.md

@@ -120,4 +120,4 @@ Option A and Option B are specified in the steps **fabric create** and **nni cre
     --ingress-acl-id "/subscriptions/xxxxx-xxxx-xxxx-xxxx-xxxxx/resourceGroups/example-rg/providers/Microsoft.ManagedNetworkFabric/accesscontrollists/example-Ipv4ingressACL" \
     --egress-acl-id "/subscriptions/xxxxx-xxxx-xxxx-xxxx-xxxxx/resourceGroups/example-rg/providers/Microsoft.ManagedNetworkFabric/accesscontrollists/example-Ipv4egressACL"
     
-    ````
+    ````