Announce the state (expanded/collapsed) of the properties panel and it's sections

[rpkoller]

Is your feature request related to a problem? Please describe
If you tab through the properties panel and try to expand or collapse the properties panel itself or one of its sections with either ctrl-option-space or just space the state an element is in is not announced (not the current state nor the state change):
https://user-images.githubusercontent.com/1665422/212553412-4bd58fcd-0014-4f29-ad44-9c73be9108eb.mov
i've tested in Camunda with macos 12.6.1 voiceover in safari (the video is recorded in) and microsoft edge. it is the same behavior with ECA in Drupal.
Even though the div that is wrapping the expanded and collapsed content already has an open attribute the state isn't announced in a screenreader so SC 4.1.2 in WCAG 2.1 isn't met that way.

Describe the solution you'd like
One option to ensure the state is announced would be by using the `aria-expanded attribute. https://www.w3.org/WAI/GL/wiki/Using_the_WAI-ARIA_aria-expanded_state_to_mark_expandable_and_collapsible_regions

Describe alternatives you've considered

Additional context

[barmac]

Thanks for reporting this issue. I think it makes sense to look into this.