Function update

Source
fn update(
    ch: &[TOCElem],
    current: LogicalLevel,
    max: SectionLevel,
    old_slides: &RwSignal<u32>,
    old_sections: &RwSignal<AllSections>,
    old_paras: &VecMap<Name, (RwSignal<u16>, u16)>,
    para_map: &VecMap<(ParagraphKind, Option<Name>), Option<Name>>,
)