Fixes for aria-live regions#9524

gonfunko wants to merge 1 commit intoRaspberryPiFoundation:add-screen-reader-support-experimentalRaspberryPiFoundation/blockly:add-screen-reader-support-experimentalfrom

microbit-matt-hillsdon:aria-livemicrobit-matt-hillsdon/blockly:aria-liveCopy head branch name to clipboard