[Docs] gnodev command in Getting Started

[Kouteki]

Description

As a Gno.land rookie ISBAT follow learning oriented, tutorial style documentation in the Getting Started section so that I could get onboarded easier.

Acceptance criteria

• Create a gnodev page in the Getting Started section
• Write a tutorial that covers use cases and steps when the gnodev command is used
• Audit all subcommands and include them in the documentation

Misc

• A great example of what tutorial style documentation looks like
• Another example of Getting Started page

Relates to #1987