Theme should follow the system

[wiiznokes]

• It doesn't work on COSMIC (it should also follow the accent color)
• make it works on other system

[wiiznokes]

For theme:

pub fn theme(&self) -> theme::Theme {
        match self {
            Self::Dark => {
                let mut t = theme::system_dark();
                t.theme_type.prefer_dark(Some(true));
                t
            }
            Self::Light => {
                let mut t = theme::system_light();
                t.theme_type.prefer_dark(Some(false));
                t
            }
            Self::System => theme::system_preference(),
        }
    }

https://hachyderm.io/@edfloreshz/112769206427407768