Fixed html5 loading issue

The html5 version of the app could lock the browser.

This was pointed out to me today here: https://github.com/jayaarrgh/BookOfShaders-Godot/issues/7

And this issue is known to the Godot project: https://github.com/godotengine/godot/issues/56670

I've uploaded the html5 export using gles2, and it seems to have resolved the issue.

Thanks for your continued support

Happy Shading!j