ChunkSize in the DefaultConfig is not S3 Compatible

[gioelecerati]

https://docs.aws.amazon.com/AmazonS3/latest/userguide/qfacts.html
S3 does not support <5MB chunk sizes, so this breaks any integration with Amazon or Google or whatever S3 implementation.

Actually, it should be possible to set up a tus.Config without the ChunkSize, unless the endpoint complains with cannot create source for stream without a finite value for the chunkSize option.