Add Showcases samples in the Sample

[jsuarezruiz]

The idea would be to add access to some showcases where:

• Replicate Dribbble or similar designs using the drawn controls.
• Take advantage of the possibilities of extension or customization of the drawn controls.

I'm thinking that maybe we could make this a kind of contest. Establish a range of dates and select from all those who send a PR with a Showcase the winner. Ideas?. https://www.bonfire.com/dotnet-maui-dark/

cc @davidortinau Do you see it possible?