I added aria-labels to both sharing links and composer, it should be deployed here in the next 10 minutes.
@MarcoZehe can you confirm it looks good?
https://github.com/discourse/discourse/commit/4191d97d48e2451ff583ed808dee081544a34d14
https://github.com/discourse/discourse/commit/4f53b85ee2bf293af6ff3e9f67f83f02700cccbe