Get appropriate data, cache, and config directories following the XDG spec, namespaced to a specific app-name subfolder.
import { XDG } from '@vltpkg/xdg'
// instantiate with the name of your thing.
const xdg = new XDG('vlt')
const cachePath = xdg.cache('some-path') // ~/.cache/vlt/some-path
const configFile = xdg.config('vlt.json') // ~/.config/vlt/vlt.json
const dataFolder = xdg.data('blah') // ~/.local/share/vlt/blah
const someState = xdg.state('foobar') // ~/.local/state/vlt/fooobar