This patch improves screenreader support by applying some basic
rules and improving the OOjs UI usage. Things done here:
- make use of 'aria-label' attribute to label interactive buttons
- use connect method on help button to allow keyboard interaction
- give hint on help button that it opens a dialog
- communicate state of autoexpand button
- add attributes to make screenreaders understand the accordion
mechanism if the slider widget
See:
https://www.w3.org/TR/wai-aria-practices/#buttonhttps://www.w3.org/TR/wai-aria-practices/#accordion
Bug: T165489
Change-Id: I7a174e5971a751ec54d4d5115d5441f0a577c103