function makeLonghand(item, data) {
  switch (item.command) {
    case 's':
      item.command = 'c';
      break;
    case 't':
      item.command = 'q';
      break;
  }
  item.args.unshift(
    data[data.length - 2] - data[data.length - 4],
    data[data.length - 1] - data[data.length - 3],
  );
  return item;
}
Converts next curve from shorthand to full form using the current curve data.

@param {import('../lib/types.js').PathDataItem} item
@param {ReadonlyArray<number>} data
@returns {import('../lib/types.js').PathDataItem}