[Bug] SettingsExpander doesn't look like WinUI's

[NotYoojun]

The current SettingsExpander:

It should look like:

[NotYoojun]

@swety2003 老哥有时间看看不，一个失败的尝试在这里：https://github.com/iNKORE-NET/UI.WPF.Modern/tree/exp_settings-expander

[NotYoojun]

Done!