Add extension https://github.com/rando-muser/sammy #212
Description
GitHub repo: https://github.com/rando-muser/sammy
Forum post: https://forum.makecode.com/t/sammy-text-to-speech-speech-synthesizer-extension/39499?u=unsignedarduino
Description: [INSERT SHORT DESCRIPTION THAT IS SIMILAR TO CURRENT DESCRIPTIONS OF EXTENSIONS - REQUIRED]