Wow! Thank you for this!! I love it 
I’ve tested it on Safari (the audio doesn’t work, I guess it’s the move on type just like IE then I presume?) and Chrome (both highlight and audio works well) ~ Mojave.
I put it on The New And Improved List Of API and Third Party Apps under Dashboard section, because I can see this script’s effect on lesson and review and kanji/vocab page. For others who can edit the wiki, feel free to edit it to make it better, like placing it to a better more specific section, maybe?
Yes, I think you should. The link is here.