Add RadioGroup

[jjenzz]

There are some significant changes to Label here for discussion. I remembered that it is invalid markup to have multiple form controls in a label (our Checkbox and Switch which render an input and a button would be invalid), so:

• I have made it a span by default with a role="label" attribute. It still does the aria-labelledby stuff so is read out fine in SRs.
• If someone passes an htmlFor attribute, it will switch to a label under the hood.
• If someone passes an as attribute, it will use whatever they pass.

Because this is now a span by default I added a click handler that will click/focus the element ref passed to the label context hook. This means we can make the label click/focus the button in these controls instead of the hidden input.

Using a span also allows us to nest labels which is useful for things like this RadioGroup where the group should have an aria-labelledby and each radio can also be labelled:

<Label>
  Favourite pet
  <RadioGroup as={Root} defaultValue="1">
    <Label>
      <RadioGroup.Item as={Item} value="1">
        <RadioGroup.Indicator as={Indicator} />
      </RadioGroup.Item>
      Cat
    </Label>{' '}
    <Label>
      <RadioGroup.Item as={Item} value="2">
        <RadioGroup.Indicator as={Indicator} />
      </RadioGroup.Item>
      Dog
    </Label>{' '}
    <Label>
      <RadioGroup.Item as={Item} value="3">
        <RadioGroup.Indicator as={Indicator} />
      </RadioGroup.Item>
      Rabbit
    </Label>
  </RadioGroup>
</Label>

I like this because it means that if you want to label something, you can just do it without worrying about structure.

[benoitgrelard]

I feel like the radio package isn't really useful on its own if we're going to offer a higher level API like radio-group.

[jjenzz]

@benoitgrelard I've moved Radio into the RadioGroup package instead

[jjenzz]

I need to reintroduce Box here too... will do that now

[jjenzz]

This is ready for you again @benoitgrelard ❤️

[jjenzz]

After a quick chat with @benoitgrelard , We've agreed to rethink the Checkbox and Radio APIs slightly and try to avoid exposing the Input since it is an implementation detail that is causing many DX issues.

[chaance]

I'm going to hold on reviewing this one until we get Checkbox merged for all the reasons you mentioned. Once we sort some of those things out, this one should be a lot simpler.

[jjenzz]

https://www.w3.org/TR/2017/WD-wai-aria-practices-1.1-20170628/examples/radio/radio-1/radio-1.html#rps_label

[chaance]

@jjenzz Just to catch me up, is this ready for me to review now? I see @benoitgrelard has approved already.

[benoitgrelard]

@chaance Yes it is, we wanted to wait for you to have a look at it.

[chaance]

Minor changes requested then GTG 👍

[jjenzz]

@chaance I think I've resolved your feedback but may have misunderstood 🙈 let me know if there's more you're hoping for here.