a11y - site setup - Addon-ons - cms ui

[Wagner3UB]

Describe the bug

• This page contains a series of accordions that are not reachable via keyboard or screen reader.

• after some tests it was discovered that using a screen reader and navigating using ctrl + alt (option) + arrows, it is possible to get to the accordion items

To Reproduce
Steps to reproduce the behavior:

1. Go to "site setup" -> "Addon-ons"
2. Navigate with the keyboard

Expected behavior

• All the accordions items need to have tabindex or be naturally found by keyboard navigation.
• The default accordion behavior (open/close) must work
• The accordion content must be reachable by the keyboard
• All items need to have a proper label to identify which will be properly identified
• All items must receive visual focus

Screenshots
If applicable, add screenshots to help explain your problem.

Software (please complete the following information):

• Volto Version 17.0.0-alpha.19
• Plone Version 6.0.4

[deodorhunter]

Work is mostly done, see #6345 for detailed changelog.
TODO: missing translations due to code splitting/changes/additions to intl messages