allow kubectl commands against all namespaces (#7637)

* allow kubectl commands against all namespaces

* enhance the readme too

plugins/kubectl/kubectl.plugin.zsh

@@ -13,6 +13,9 @@ fi
 # This command is used a LOT both below and in daily life
 alias k=kubectl
 
+# Execute a kubectl command against all namespaces
+alias kca='f(){ kubectl "$@" --all-namespaces;  unset -f f; }; f'
+
 # Apply a YML file
 alias kaf='kubectl apply -f'