Using a smaller block size

Hi,

First of all thanks for setting up this package :) It's super helpful, thanks

I'm wondering, is there a way to use a smaller block size ? I tried modifying the python code so that no errors are thrown, however I'm hitting a

`RuntimeError: CUDA error: an illegal memory access was encountered`

error when calling the cuda kernel. I tried to look a bit into the kernel code, and it seems that the `block_size` argument [is not used](https://github.com/huggingface/pytorch_block_sparse/blob/e71b54273a25ecebd2aa57181d87664e5de98dc3/pytorch_block_sparse/native/block_sparse_cutlass_kernel.cu#L121). So I'm curious how the kernel knows to expect a minimal size of 32.

Any clarifications would be super helpful!

Thanks