I like your project, but I'd like it more if it was accompanied by a video of the text being highlighted as it is being read (a kind of dual modality reading - visual + audio). I created such a tool for myself on MacOS with the Alex voice, that works in browsers on any page and in PDFs. I find dual modality reading to enhance my focus a lot. Btw, I use this tool to read this very thread of comments.

And of course I would want to hear the amazing Wavenet voices used in this role.