Update to Rivet 2.8.1

Problem/Motivation

We’re currently using Rivet 2.7.0. There have been two releases (2.8.0 and 2.8.1) containing several Accessibility and Bug fixes – some of which I provided to the Rivet team back in May and June.

Proposed resolution

• Bump the Rivet library dependency to the latest version (2.8.1) in the Drupal theme upstream.
• Update our code following the documented manual changes mentioned on release notes of 2.8.0 and 2.8.1
  • 2.8.1
    • Breadcrumbs - The aria-label="Current page" attribute on breadcrumbs components has been updated to aria-current="page" We’ll need to manually update breadcrumbs markup in the Rivet theme after updating to Rivet 2.8.1.
      • https://github.com/indiana-university/rivet-source/issues/756
  • 2.8.0
    • Select2 Dropdowns - A duplicate focus-ring highlight on hover of the active dropdown links was removed in Rivet 2.8.0. The Rivet Drupal theme is mimicing this Rivet style in a custom Select2 integration for Webforms, so we'll need to review and update our webform integration styles accordingly.
      • https://github.com/indiana-university/rivet-source/pull/759
    • The following 3 bug fixes have workarounds in the Rivet theme that need to be removed because they’ve been fixed upstream:
      • Fixed issue with spacing utilities not working with rows containing loose or tight columns
        • https://github.com/indiana-university/rivet-source/pull/751
      • Fixed styling of series nav component when showing only a link to the previous entry
        • https://github.com/indiana-university/rivet-source/pull/758
      • Updated prose utility to not erroneously hide images, line breaks, and other void elements
        • https://github.com/indiana-university/rivet-source/pull/754