XAUTHORITY environment variable not accounted for

[TressaDanvers]

It is standard practice for a display manager to first check if the XAUTHORITY environment variable is set before creating an Xauthority file. If it is not set, then the default of $HOME/.Xauthority should be used, but if it is set then whatever file, for example $XDG_RUNTIME_DIR/Xauthority, or $XDG_CACHE_HOME/X11/Xauthority, should be used instead. Currently this application does not follow this convention.

[h-leth]

I have opened a pull request on this issue, ~~it's a draft for now. Have some TODO's~~

Let me know if anything needs to be fixed.