Both versions are available here!
It's definitely not for lack of wanting to add a a way to delete individual saves. It's just that it is, at the very least, almost impossible. In short, with the way the engine's creator(s) built it, it would be a lot simpler for me to rebuild the entire game in a new engine than it would be to hack in this one feature to the existing game's code.
My apologies, I forgot you were using the HTML version! In that case, the local storage folder location depends on the browser that you are using to play the game.
If you are using Chrome, I believe it should be in :
~/Library/Application Support/Google/Chrome/$PROFILE/Local Storage
If Safari, that should be:
~/Library/Safari/LocalStorage
First I'll note that if you ever want to try and pull up these saves again, first back up the entire Artifact local storage folder somewhere else on your hard drive.
Then, you can delete the entire Artifact folder in this local storage (since this local storage folder is a completely separate location from the actual installation folder, meaning you won't have to redownload or reinstall anything), and then it's going to automatically be created anew the next time you run the game.