TTS implementation(s) of DPUB-ARIA

Hi @mattgarrish ! I was reading through #55 and was wondering if I may ask a clarifying comment on the TTS remarks there?

Is there an existing reference implementation for text-to-speech that takes DPUB-ARIA markup as input? Or maybe even better - an actively developed open project that aims to be a reference implementation? I am currently looking for a conforming TTS engine that I can use for testing the outputs of our generator for HTML/ePub formatted STEM documents.

My context: I am investigating the existing markup strategies for STEM accessibility and naturally encountered the [DPUB-ARIA](http://kb.daisy.org/publishing/docs/html/dpub-aria/) spec pages. In particular, I am interested in improving the accessibility of [ar5iv](https://ar5iv.labs.arxiv.org/), which I maintain, and our generator tool [latexml](https://github.com/brucemiller/LaTeXML/), respectively.

If I can anchor into a reliable TTS engine that has significant support for DPUB-ARIA, that could make life for us much easier. Would you be able to offer a broad overview of implementations as of mid-2023?

Thank you!