Add macro-level ‘selected’ option for radios

[vickytnz]

At some point we should also add copy GOV.UK and let you set value: on the top-level macro option for radios, to save having to set checked on each individual item, as that’d be far simpler.

Originally posted by @frankieroberto in nhsuk/nhsuk.service-manual.prototype-kit.docs#20 (comment)

[frankieroberto]

@vickytnz have moved this to the repo for NHS Frontend itself as it’s not part of the prototype kit.