Update readme & demo for `Show-ObjectTree`

[tig]

Prerequisites

• Write a descriptive title.
• Make sure you are able to repro it on the latest version
• Search the existing issues.

Steps to reproduce

n/a

Expected behavior

Readme & demo illustrate Show-ObjectView

Actual behavior

Readme & demo don't illustrate Show-ObjectView

Error details

No response

Environment data

n/a

Version

7.5

Visuals

No response