Update documentation to include committer add format

[RandomAshes]

Feature Request

Description

Presently the documentation doesn't tell the user what to add after guet add.

Example

Documentation and guet help should show the user to write out the following:

guet add initials "Full Name" email@mail.com

Note:

It could also be helpful to show examples of how to use guet set: guet set ac cb for example