Details block > add radius support

[Marc-pi]

What problem does this address?

In case we make use of the the Details block for a FAQ for instance
... we can define the background of the details, the border color also,
but not the radius !

What is your proposed solution?

Add radius support below the border area

WP6.7RC4 / GB 19.6.0

[hanneslsm]

Just want to add that I just needed the border radius for the details block. I have defined it globally via the theme.json but would rather specify the radius only on certain blocks.
So it works globally, but there is need for solving this issue.