fix: card border radius

[lukewalczak]

Summary

Fix Card and Card.Cover border radius

ios	android	web

Related issue

• Card Roundness #3460

Test plan

Added unit tests.

[github-actions]

The mobile version of example app from this branch is ready! You can see it here

.

[stefano-vergani]

Hi, can't make border radius 0 on card cover using inline style or Stylesheet.create. I applied:
`
borderBottomEndRadius: 0,

    borderBottomStartRadius: 0,

    borderTopEndRadius: 0,

    borderTopStartRadius: 0,

    borderBottomRightRadius: 0,

    borderBottomLeftRadius: 0,

    borderTopRightRadius: 0,

    borderTopLeftRadius: 0,

    borderRadius: 0`

but no luck. Am i wrong?

[BMTCompany2]

@stefano-vergani Did you ever figure this out? I don't want a rounded card cover either