examples: updated l2sm-network use guide

Following recent changes around the usage of l2sm-network, the ping pong example has been updated to showcase how the networks are defined

examples/ping-pong/network.yaml

-apiVersion: "k8s.cni.cncf.io/v1"
-kind: NetworkAttachmentDefinition
+apiVersion: l2sm.k8s.local/v1
+kind: L2SMNetwork
 metadata:
   name: ping-network
 spec:
-  config: '{
-      "cniVersion": "0.3.0",
+  type: vnet
\ No newline at end of file
-      "type": "l2sm"
-    }'

examples/ping-pong/ping.yaml

@@ -5,7 +5,7 @@ metadata:
   labels:
     app: ping-pong
   annotations:
-    k8s.v1.cni.cncf.io/networks: ping-network
+    l2sm/networks: ping-network
 spec:
   containers:
   - name: router
@@ -15,4 +15,4 @@ spec:
       capabilities:
         add: ["NET_ADMIN"]
   # Use this parameter if you want to place the pod in a specific node
-  #nodeName: masterk8s
+  nodeName: l2sm1