[Gradient Compression] Add a documentation page for DDP communication hooks (#51715)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/51715
Add a documentation page for DDP communication hooks.
Screenshot:
{F369781049}
Test Plan: View locally
Reviewed By: pritamdamania87
Differential Revision: D26249330
fbshipit-source-id: ab973390ddb785c5191f587a1b2b6de7d229e50e
