I more or less fixed it. I add this to add sound:
<audio src="website.net/sounds/testsound.wav" autoplay />
Only problem: I don't know how to upload sound or embed it.
The only sounds I got to work were on this site. You click on a sound effect and it takes you to a file on an HTML sound player. I can't for the life of me find any other site like this, let alone upload sounds to an HTML player.
Finally fixed it. Just paste this into a message:
<audio autoplay="auto"> <source src="(google drive download link here)"> </audio>
I used google drive to upload a sound, and copied the download page into where it says (google drive download link here.) There's a slight delay but that's fine.
You can also include sound files in your game; but there's a file size limit and it may be a little hassle to do.
Somehow I fixed the delay without even trying. I was going about my game-making business, looking for a YouTube to mp3 audio cutter, when I came across this website. It turns out, this website generates a link for your audio file! What you need to do is paste a YT link, cut it to your desired length (if you don't want to cut it, just put the start point at the start of the video and the endpoint at the end,) MAKE SURE YOU HAVE IT SELECTED TO MP3, converting it, and then click download. It doesn't download it, instead, it plays it in an HTML player! Hope this helps anyone who's having the same issue as I was.