docs: deprecate exec-cronjob in favor of kubctl create

Author: etiennetremel

README.md

@@ -39,6 +39,13 @@ Options:
 
 ### Exec cronjob
 
+> DEPRECATION NOTICE:
+> This plugin isn't necessary anymore, the kubectl cli let you create
+> cronjob with the create subcommand:
+> ```
+> $ kubectl create job --from cronjob/my-cronjob my-job
+> ```
+
 ```bash
 # install the exec-cronjob plugins
 $ kubectl krew install exec-cronjob

exec-cronjob/kubectl-exec_cronjob.sh

@@ -5,6 +5,12 @@
 set -e
 
 function usage() {
+  echo "DEPRECATION NOTICE:"
+  echo "This plugin isn't necessary anymore, the kubectl cli let you create"
+  echo "cronjob with the create subcommand:"
+  echo "    kubectl create job --from cronjob/my-cronjob my-job"
+  echo ""
+  echo ""
   echo "Run a CronJob immediately as Job by extracting the Job spec and"
   echo "creating a Job instance thereof."
   echo ""