async function onItemsSelectedTrigger(e) {
  PropertiesService.getUserProperties().setProperty(
    "selectedItems",
    JSON.stringify(e.drive.selectedItems)
  );
  return (await card(e.drive.selectedItems)).build();
}
Build a simple card that checks selected items' quota usage. Checking
quota usage requires user-permissions, so this add-on provides a button
to request `drive.file` scope for items the add-on doesn't yet have
permission to access.

@param e The event object passed containing contextual information about
   the Drive items selected.
@return {Card}