added docs to nn.rst (#48374)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/48198
Added following functions to a subsection "Global Hooks For Module" in containers sections of nn.rst.
- register_module_forward_pre_hook
- register_module_forward_hook
- register_module_backward_hook
screenshots:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48374
Reviewed By: ejguan
Differential Revision: D25219507
Pulled By: albanD
fbshipit-source-id: 0dd9d65f562c001c993ebcb51465e8ddcf631231
