Include missing cert export step

Updating the instructions to include missing step of getting issued cert exported from kubernetes, decoded, and ready for kubeconfig setup.

content/en/docs/reference/access-authn-authz/certificate-signing-requests.md

@@ -252,6 +252,12 @@ kubectl get csr/john -o yaml
 
 The certificate value is in Base64-encoded format under `status.certificate`.
 
+Export the issued certificate from the CertificateSigningRequest.
+
+```
+kubectl get csr john -o jsonpath='{.status.certificate}'| base64 -d > /home/vagrant/work/john.crt
+```
+
 ### Create Role and RoleBinding
 
 With the certificate created. it is time to define the Role and RoleBinding for