Add the Material Sliver widgets to the widget catalog

[sfshaza2]

Page URL

https://docs.flutter.dev/ui/widgets

Page source

No response

Describe the problem

The Cupertino sliver widgets are added but. not the Material sliver widgets. Add them to the Scrolling category or maybe create a Sliver category

Expected fix

No response

Additional context

No response

I would like to fix this problem.

• [ ] I will try and fix this problem on docs.flutter.dev.