text: Title: Mention NVIDIA non-commercial in top LICENSE section
  Body: Could you mention NVIDIA license, which is written in encoders/mix_transformer.py, in the top LICENSE section?
  
  This can cause a problem for commercial use including Kaggle, in which the competition rule often requires commercial use. I misunderstood that segFormer had become completely MIT.
  
  For example, mmcv has a LICENSES page, which lists files with NVIDIA license.
  https://github.com/open-mmlab/mmcv/blob/main/LICENSES.md
  
  Thanks for developing and maintaining this great library! I am using a lot for Kaggle.
  