docs/zh_CN: add disclaimer file

This a disclaimer file which will be included in Chinese files
as header. To reduce the same common contents copy.

Part of contents quoted from Federico Vaga's file:
    Documentation/translations/it_IT/disclaimer-ita.rst.
Thanks a lot!

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Harry Wei <harryxiyou@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Shawn Guo <shawn.guo@linaro.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Coly Li <colyli@suse.de>
Cc: Federico Vaga <federico.vaga@vaga.pv.it>
Signed-off-by: Weiwei Jia <harryxiyou@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>