[deploy] docs (#69251)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69251
This adds some actual documentation for deploy, which is probably useful
since we told everyone it was experimentally available so they will
probably be looking at what the heck it is.
It also wires up various compoenents of the OSS build to actually work
when used from an external project.
Differential Revision:
D32783312
D32783312
Test Plan: Imported from OSS
Reviewed By: wconstab
Pulled By: suo
fbshipit-source-id: c5c0a1e3f80fa273b5a70c13ba81733cb8d2c8f8
