doc/zh_CN: add cpu-load Chinese version

Add cpu-load Chinese version and link it into admin-guide.
Based on Alex's recent thread:

  https://lkml.kernel.org/r/20200713115807.56362-1-alex.shi@linux.alibaba.com



Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Tao Zhou <ouwen210@hotmail.com>
Link: https://lore.kernel.org/r/BL0PR14MB37798BBF2307910DE73EF6D49A770@BL0PR14MB3779.namprd14.prod.outlook.com


Signed-off-by: Jonathan Corbet <corbet@lwn.net>