StateBand
A band showing state changes.
const band = new StateBand(timeline);
band.label = 'States';
band.states = [
{ time: -Infinity, label: 'A' },
{ time: 30, label: 'B' },
{ time: 40, label: 'C' },
{ time: 60, label: null }, // Gap
{ time: 80, label: 'D' },
];