Missing tag format for 'add' command in user guide

[zengzihui]

In the user guide, the format provided for add command does not consist of the tag field. However, in the Tip box, it says a person can have any number of tags, including 0.

I feel the format to add tag to the person should be documented in the user guide if it is an optional field.

The format stated here is also different from the format stated at the Command summary.