add-lightly-train-to-training-frameworks-readme (#2474)

Author: yutong-xiang-97

README.md

@@ -598,6 +598,7 @@ One of the greatest assets of PyTorch is the community and their contributions.
 
 ### Training / Frameworks
 * fastai - https://github.com/fastai/fastai
+* lightly_train - https://github.com/lightly-ai/lightly-train
 
 ## Licenses