[Feature Request]: Replace bottom padding on checkbox and radio item with calculated bottom margin.

[bdfranck]

Is your feature request related to a problem? Please describe

In my previous PR for the checkbox component (#1869), I used bottom padding to match the radio item.

padding-bottom: var(--goa-space-m);

But I've since noticed a much better approach used by other components: set a default calculated margin.

export let mb: Spacing = "m";

This approach gives teams more flexibility to adjust or remove the bottom margin as needed. They can set the mb property instead of relying on negative margins.

Describe the solution you'd like

1. Add calculated margins to the radio item component
2. Replace the bottom padding from the checkbox and radio item with a calculated bottom margin: export let mb: Spacing = "m";

Are you able to assist to bring the feature to reality?

Of course! I've created an initial PR for the idea: #1967