Not an extension per-se, but:
- Windows has a built-in screen reader which you can trigger with a keyboard shortcut to read highlighted text. Enable Reader-Mode in your browser, then just ctrl-a the text and follow that with the voice narrator shortcut.
- Alternatively, you could look into NVDA - no, not NV[I]D[I]A. NVDA is a screen reader written in python - chances are, it has a feature that can solve the thing you are looking for. If it can not, I am sure people there can point you in a good direction, as most users of NVDA are blind and heavy TTS users - so, chances are, they have seen a thing or two. Or...well, heared. o.o
NVDA: https://github.com/nvaccess/nvda