Accordion multiselectable option not working

Problem/Motivation

The option "Allow more than one item to expand at a time" has no effect.

Steps to reproduce

1. Add an Accordion paragraph type to a content node.
2. Select "Allow more than one item to expand at a time."
3. Add at least two accordion items.
4. Save the node.
5. Try opening multiple accordions.

Proposed resolution

Add the following two lines after $variables['attributes']['aria-multiselectable'] = 'true'; (Line 259) in uswds_paragraphs.module:

$variables['attributes']['data-allow-multiple'] = TRUE;

$variables['attributes']['class'][] = 'usa-accordion--multiselectable';