fix(copybuffer): show error below the command line

plugins/copybuffer/copybuffer.plugin.zsh

@@ -5,7 +5,7 @@ copybuffer () {
   if which clipcopy &>/dev/null; then
     printf "%s" "$BUFFER" | clipcopy
   else
-    echo "clipcopy function not found. Please make sure you have Oh My Zsh installed correctly."
+    zle -M "clipcopy not found. Please make sure you have Oh My Zsh installed correctly."
   fi
 }