Update README.md

Docs/README.md

 # Links to Our Documents
-- [Our Progress](./OurProgress/)  
-- [Proxy Cost](./ProxyCost/)
-- [Code Elements](./CodeElements/)
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+- [Our Progress: A Chronology](./OurProgress/) provides latest updates and is periodically synched to [this Google Doc](https://docs.google.com/document/d/1HHZNcid5CZvvRqj_njzF7hBhtNSpmRn3fCYniWNYBiY/edit).
+- [Proxy Cost](./ProxyCost/) documentation gives implementation details to enable reproduction of the wirelength, density and congestion costs used by [Circuit Training](https://github.com/google-research/circuit_training).
+- [Code Elements](./CodeElements/) documentation gives implementation details to enable reproduction of the gridding, gruoping and clustering used by [Circuit Training](https://github.com/google-research/circuit_training).