introducing a radio button component and a radio button group component

[daviddkkim]

Closes #580

Changes

// Describe what you changed

I introduced a radio button and radio button group as indicated in issue #580.
@jrenee42 - I didn't see that you assigned yourself to the issue until just now. This isn't quite done yet (no color options, .. etc) but I just thought I'd submit what I have in hopes that it can be helpful. If not, no worries - feel free to squash this PR!

One notable offshoot is that Instead of taking the array of string values for labels as you suggested, I have it so that it accepts children radio buttons. I started with the singular Radio button so I thought this would allow me to use that to the fullest.

Screenshots

// Add screenshots here if relevant

Checklist

Check all that apply

• Updated documentation to reflect changes
• Added entry to top of Changelog with link to PR (not issue)
• Tests pass
• Peer reviewed and approved
• Signed CLA (if not already signed)

[daviddkkim]

In terms of margin, button size, font size, .. etc, I followed the exact style guide as is but the contrast in the size of radio input and the font feels odd to me. I didn't want to diverge from the style guide and introduce arbitrary styling so I left it as is.