Anki add-on: TTS - Get text localStorage.getItem and read by spai

Read text using sapi stored in window.localStorage.getItem. (This plugin does not cover how to store text in window.localStorage. Usually, JavaScript is used in templates to store text in window.localStorage.) Limitations: Since sapi is used, it only works on Windows. Use an external command called "balcon.exe". (It is more stable than writing it in Python directly.)