Add documentation about storage sharing is preserved and serialized f… (#40412)
Summary:
…ile size.
fixes https://github.com/pytorch/pytorch/issues/40157
Pull Request resolved: https://github.com/pytorch/pytorch/pull/40412
Reviewed By: ezyang
Differential Revision: D22265639
Pulled By: ailzhang
fbshipit-source-id: 16b0301f16038bd784e7e92f63253fedc7820adc
