DataLoader docs update to describe how workers are managed, including Windows. (#18091)
Summary:
It's been hard to understand how workers are launched and what code runs in the worker vs. main process, especially on Windows, which leads to many of our samples failing. This explains when workers run an how to make code work on Windows as well.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18091
Differential Revision: D15083766
Pulled By: soumith
fbshipit-source-id: 8a7e60defc8a72ec63874f657d7d5267d951dccf
