--all-namespaces shorthand

As a beginner to kubectl, I must have typed (and re-typed due to typos) --all-namespaces many hundreds of times before I stumbled across the -A shorthand notation for this.  I sincerely would be grateful on behalf of all kubectl beginners if this very useful cheat could be added to this cheatsheet.  I have proposed in this PR a location quite near the beginning of the cheatsheet for this so that it is very hard to miss.

content/en/docs/reference/kubectl/cheatsheet.md

@@ -38,6 +38,11 @@ complete -F __start_kubectl k
 source <(kubectl completion zsh)  # setup autocomplete in zsh into the current shell
 echo "[[ $commands[kubectl] ]] && source <(kubectl completion zsh)" >> ~/.zshrc # add autocomplete permanently to your zsh shell
 ```
+### A Note on --all-namespaces
+
+Appending --all-namespaces happens frequently enough where you should be aware of the  shorthand for --all-namespaces:
+
+```kubectl -A```
 
 ## Kubectl context and configuration