Add bdr prop - border radius property in <Box/> component

[Gaurav-Verma07]

Currently it supports bd which sets the border of the box but lacks any prop to set the border-radius

[ryuhangyeong]

In this situation, I think it makes sense to use the <Paper /> component.

Internally it uses the <Box /> component.

<Paper radius={rem(20)} withBorder bd={"1px solid red"}>
  Mantine
</Paper>