extend documentation of "CZIcmd"

[ptahmose]

Is your feature request related to a problem? Please describe. c.f. https://github.com/ZEISS/libczi/pull/20#discussion_r1051379677

Describe the solution you'd like

• all commands should be described in the documenation
• in best case - they should come with "ready-to-run examples"
• one challenge here - how to provide/make available "sample data"

Describe alternatives you've considered N/A

Additional context N/A