Hey, no, you’re right. The engine doesn’t provide any tools for sound. In order to add sound you’ll need to learn about how sound works in HTML and/or JavaScript. One library you might look into for this is Howler.js.
No worries at all! If you're interested, I'd encourage you to check out at how the sound was implemented for the demo here: https://github.com/okaybenji/text-engine/blob/itch/custom/audio.js
It's pretty straightforward, so definitely take a look if you're wanting to do something similar. I can help with this to some extent, so just let me know if you have any questions about it.