allow different batch sizes

[pilosoposerio]

this is for an enhancement.

aside from setting a specific batch size for all splits, let users set a batch size per split file that will be generated.

revision in the main code can be something like this:

try:
	page = 0 # nth fragment
	origBatch = batch

	while True:
		data: List[Dict[str, Any]] = []

		batch = origBatch
		
		if batches is not None and page < len(batches):
			batch = batches[page]
			page += 1

		for _ in range(batch):
			data.append(next(features))
		
		yield geojson.FeatureCollection(data)
except StopIteration:

originally, my aim is to have a file size limit per split... but this can do for now.