I'm currently trying to get comfortable on NixOS on my laptop before switching over to it from Arch on my desktop, and I've noticed that there's a .keep file in the ~/.cache directory. I normally wouldn't care about it, except that my XDG_CACHE_HOME isn't ~/.cache, but rather set to $XDG_STATE_HOME/cache which is ~/.var/cache (to mirror how cache is in /var/cache).
So what even is the .keep file, and how do I make it go to my XDG_CACHE_HOME to stop it from cluttering up my home directory?