Consider using XDG_CONFIG_HOME

Would you consider moving the default, or at least supporting, $XDG_CONFIG_HOME/vja rather than $HOME/.vja?

I have found the VJA_CONFIGDIR environment variable which I have set to $XDG_CONFIG_HOME/vja for my setup, although i don't think that is documented anywhere.

Happy to make a Merge request if it's something you are interested in