Supporting $XDG_DATA_HOME

[hch12907]

Dirs provided 3 paths (bin_home, cache_home, config_home) as of now.
How about adding a new path for $XDG_DATA_HOME?
It defaults to $HOME/.local/share on Linux. (For Windows, I think it would be the best to default it to C:\ProgramData ... nevermind, I think <User>\AppData\Local is better.)

[tbu-]

Do you also have an idea where to put it for macOS?

[hch12907]

I'd suggest ~/Library/Application Support or ~/Library/Preferences/, but I have never owned an OSX machine to confirm these.