Update README-zh with adding required storage to download script

Added a bash command example for downloading RoboCOIN dataset.

Author: liu-xuecheng

README_zh-CN.md

@@ -75,6 +75,7 @@ pip install robocoin
 
 ```bash
 # you can copy the bash command from the website and paste it here, such as:
+# Required storage:  10.8GB.
 robocoin-download --hub huggingface --ds_lists Cobot_Magic_move_the_bread R1_Lite_open_and_close_microwave_oven
 
 # the default download path is ~/.cache/huggingface/lerobot/, which will be used as default dir of LerobotDataset.