[form-schema] Make rjsf description prop available to components

[kriscooke]

Proposed Changes

• form-schema passes through rjsf's optional description prop for use by form input components in component-library
• theme styling enabled for description labels
• description controls added to Storybook

Related to #359

Needs work:

• [ ] HTML-only case does not yet render description labels (Storybook problem only)
• styling across the different input components (esp. in the Button theme)
• double-check accessibility good practice on description labels

[wenzowski]

Fantastic start! As far as accessibility goes, let's make sure to update the storybook so the manual axe checks can run? (not a full answer...but something that should at least be checking the font size and color of the new descriptions).

[wenzowski]

Each LABEL element is associated with exactly one form control.

This will produce two sibling labels for the same input id. Maybe we could consider wrapping the description into a <label>{title}<span>{description}</span></label> inside the existing label tag?

Alternatively, we could wrap labels around inputs, but this might be a breaking change:
<label>{title}{description}<input /></label>

[kriscooke]

Exactly what I was thinking in the back of my head, will play around with this...

Each LABEL element is associated with exactly one
form control.