Function checkbox 

pub fn checkbox<State, F>(
    checked: bool,
    label: impl Into<String>,
    on_toggle: F,
) -> CheckboxView<State>
where
    State: 'static,
    F: Fn(&mut State, bool) + 'static,

Create a checkbox reflecting checked, labelled label, that fires on_toggle(state, !checked) on release inside its bounds.