Add publish Journey stage to main README

[antoniivanov]

What is the feature request? What problem does it solve?

Publish (also called export) use cases are important for users of VDK and we should show case them in main README.

Suggested solution

Implement design from https://www.canva.com/design/DAFnq9ouriY/FxmviN90b9ofU5EvNV5HLQ/view#5 in README.md