### What changes were proposed in this pull request?
adding user guide to README for cli
### Why are the changes needed?
better user experience when using CLI.
### Does this PR introduce _any_ user-facing change?
no
### How was this patch tested?
N/A
Closes#2862 from akpatnam25/CELEBORN-1678.
Authored-by: Aravind Patnam <akpatnam25@gmail.com>
Signed-off-by: mingji <fengmingxiao.fmx@alibaba-inc.com>
