macOS Support (#18)

* replace target_os = "linux" with target_family = "unix"

* check correct dir for macos steam files

src/gog/gog_settings.rs

@@ -5,6 +5,6 @@ pub struct GogSettings {
     pub enabled: bool,
     pub location: Option<String>,
     pub wine_c_drive: Option<String>,
-    #[cfg(target_os = "linux")]
+    #[cfg(target_family = "unix")]
     pub create_symlinks: bool,
 }