add pypi badge to README (#51)

Author: d4l3k

README.md

@@ -13,7 +13,10 @@ Easy Per Step Fault Tolerance for PyTorch
   | <a href="https://pytorch-labs.github.io/torchft/"><b>Documentation</b></a>
   | <a href="https://github.com/pytorch-labs/torchft/blob/main/media/fault_tolerance_poster.pdf"><b>Poster</b></a>
   | <a href="https://docs.google.com/document/d/1OZsOsz34gRDSxYXiKkj4WqcD9x0lP9TcsfBeu_SsOY4/edit"><b>Design Doc</b></a>
-  |
+  | 
+</p>
+<p align="center">
+  <a href="https://pypi.org/project/torchft-nightly/"><img alt="PyPI - Version" src="https://img.shields.io/pypi/v/torchft-nightly"></a>
 </p>
 
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