add echo message for check_zsh_polyjuice

zsh/functions/check.sh

@@ -45,6 +45,8 @@ function check_zsh_polyjuice() {
     if (( ! $+commands[python3] )); then
         echo "python3 is not installed."
     fi
+    
+    echo "Using `install_plugins` function to install missing plugins."
 }
 
 function check_tools() {