Fix the KitchenSink page on v8.0.0-major

[alex-page]

• Fixed rendering of the page with Update index.ts to include CustomProperties #4744
• contextual save bar, and topbar are stuck to the top of the page instead of rendering where they should be

[kyledurand]

Another problem with kitchen sink on v8 is that the contextual save bar, and topbar I believe, are now stuck to the top of the page instead of rendering where they should be. Probably due to my changes. I can look into it next week