pub fn config_base_dir() -> Option<PathBuf>Expand description
Resolves the per-user base directory for an app’s config and data files.
Returns $XDG_CONFIG_HOME when set, else the platform-idiomatic default:
$HOME/Library/Application Support on macOS, %APPDATA% on Windows, or
$HOME/.config elsewhere. Only absolute paths are accepted; a relative
value is rejected so files never land relative to the current working
directory.