Add .radio-group component

[simurai]

This adds the .radio-group component from dotcom.

📖 Docs Preview

TODO

• Add styles from dotcom
• Add documentation
• Adjust spacing

TODO on dotcom

• Remove radio-group.scss https://github.com/github/github/pull/128984

/cc @primer/ds-core

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[simurai]

Refactor?

Was thinking of also making this a "checkbox group". Maybe without showing the checkboxes? For use cases where multiple selections should be possible:

And would be nice if the radio/checkbox can also be inside the <label> so that it's not necessary to add these id and fors.

Maybe one day ™️ ?

[simurai]

Ok, changed the spacing to match the height (34px) of other inputs and buttons:

If we wanted to get rid of the "disables", we probably should change the height on all components that get used next to each other.

[simurai]

Awesome, thank you! #979 (comment)

Ok, I'll count this as a 👍 and merge it. 🚢