feat: Add initial support for screen readers (experimental)#9280

BenHenning merged 4 commits intoRaspberryPiFoundation:add-screen-reader-support-experimentalRaspberryPiFoundation/blockly:add-screen-reader-support-experimentalfrom

BenHenning:introduce-initial-screen-reader-supportBenHenning/blockly:introduce-initial-screen-reader-supportCopy head branch name to clipboard