Please write configuration files to XDG_CONFIG_HOME

[Elinvention]

In the GNU/Linux world there is this convention of keeping program's configuration files in $XDG_CONFIG_HOME which defaults to $HOME/.config/ if not set. See https://wiki.archlinux.org/index.php/XDG_Base_Directory.

Some programs do create a folder in the user's home directory, but a least with a dot prepended, so that they are hidden by most file managers. mqtt-spy instead creates 2 visible files and a directory in the home directory, which is annoying.