merge = (targetSet, toMerge) => {
	for (const set of toMerge) {
		for (const item of set) {
			targetSet.add(item);
		}
	}
}
@template T
@param {Set<T>} targetSet set where items should be added
@param {Set<Iterable<T>>} toMerge iterables to be merged
@returns {void}