kubectl: add README (#7258)

plugins/kubectl/kubectl.plugin.zsh

@@ -38,7 +38,7 @@ alias kdp='kubectl describe pods'
 alias kdelp='kubectl delete pods'
 
 # get pod by label: kgpl "app=myapp" -n myns
-alias kgpl='function _kgpl(){ label=$1; shift; kgp -l $label $*; };_kgpl'
+alias kgpl='kgp -l'
 
 # Service management.
 alias kgs='kubectl get svc'
@@ -104,4 +104,4 @@ alias kcp='kubectl cp'
 alias kgno='kubectl get nodes'
 alias keno='kubectl edit node'
 alias kdno='kubectl describe node'
-alias kdelno='kubectl delete node'
\ No newline at end of file
+alias kdelno='kubectl delete node'