Add __init__.py for group wise lut quantization package (pytorch#2702)

Summary: Pull Request resolved: pytorch#2702

Reviewed By: metascroy

Differential Revision: D79119958

Author: szyszyzys

torchao/prototype/quantization/codebook_groupwise/__init__.py

@@ -0,0 +1,4 @@
+from .codebook_quantized_tensor import GroupwiseLutQuantizedTensor
+from .api import GroupwiseLutWeightConfig
+
+__all__ = ["GroupwiseLutQuantizedTensor", "GroupwiseLutWeightConfig"]