UHF-8136 accordion accessibility

[rpnykanen]

UHF-8136

What was done

• Changes based on accessibility report
• Fixed bug causing error when loading a page with non existing anchor link

How to install

• Make sure your instance is up and running on latest dev branch.
  • git pull origin dev
  • make fresh
• Update the HDBT theme
  • composer require drupal/hdbt:dev-UHF-8136_accordion_accessibility
• Run make drush-cr

How to test

• Go to a page with accordion

  • Add gibberish as anchor link (#qwerty) and reload the page
  • Check inspector for javascript errors. No errors should emerge from accordion library.

• Test accessibility:

  • Hidden span (with "toggle accordion" -text for screen readers) should br removed from accordion item header
  • Aria-labelled-by removed from toggle button
  • Aria-expanded removed from close button
  • Close button's "keypress" or "mouseup" event should transfer the focus back to the accordion item's toggle button

• Check that this feature works

• Check that code follows our standards

Designers review

• This PR does not need designers review
• This PR has been visually reviewed by a designer (Name of the designer)

Other PRs

• Link to other PR