Add FreeGrad library (#144)

* Add FreeGrad library

* Update README.md

Author: tbox98

README.md

@@ -711,6 +711,8 @@ Janai, J., Güney, F., Ranjan, A., Black, M. and Geiger, A., Unsupervised Learni
 343. [SSSNET](https://github.com/SherylHYX/SSSNET_Signed_Clustering): Official implementation of the SDM2022 paper "SSSNET: Semi-Supervised Signed Network Clustering".
 344. [MagNet](https://github.com/matthew-hirn/magnet): Official implementation of the NeurIPS2021 paper "MagNet: A Neural Network for Directed Graphs".
 345. [Semantic Search](https://github.com/kuutsav/information-retrieval): Latest in the field of neural information retrieval / semantic search.
+346. [FreeGrad](https://github.com/tbox98/FreeGrad) - PyTorch library for custom backward passes, straight-through estimators and gradient transforms.
+
 
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