Function map_keyed 

pub fn map_keyed<T, K, V>(
    list: ReadSignal<Vec<T>>,
    key_fn: impl Fn(&T) -> K + 'static,
    view_fn: impl Fn(ReadSignal<T>) -> V + 'static,
) -> View
where
    T: Clone + PartialEq + 'static,
    K: Eq + Hash + Clone + Display + 'static,
    V: IntoView + 'static,