Follow XDG Base Directory for cfgFile

[Ratakor]

According to the XDG Base Directory Specification we should check the XDG_CONFIG_HOME environment variable before assuming that it is $HOME/.config. Thus we should check this variable then assign cfgFile to it + "/baton.json" or continue with the current behavior if it doesn't exist.

This might be useful for the implementation instead of using homedir.

[Ratakor]

Somehow I made a CLI very similar to baton but faster that supports this specification.
If anyone is interested it's here.