Indicate selection as required?

[andomain]

Great component!
Was just thinking it would be cool to maybe include some way of duplicating the 'required' functionality within a static HTML5 form? The bare minimum is one of the radio inputs within a namespace/group having the attribute but it is suggested they all have it just just for consistency.
This can be currently achieved by adding the required attribute to the <Radio> children nodes, however it would be nice to specify it on the RadioGroup to match all the other API props?

Happy to look into this and create a PR if you agree?