I have a SvelteKit website deployed with Github Pages. All it shows is this:

The path is https://username.github.io/src/index.html. (I renamed app.html to index.html because routing to https://username.github.io/src/app.html didn't work for some reason).
Why is it not working? Is it because I renamed app.html to index.html? If that's the case then what should I do?
You have to build the application using the static adapter and then deploy those built files to the GH pages branch. See these docs for more info (note also the extra section on GH pages).