Add reference documentation for torch/library.h (#41470)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/41470
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Test Plan: Imported from OSS
Reviewed By: zou3519
Differential Revision: D22577426
Pulled By: ezyang
fbshipit-source-id: 4bfe5806061e74181a74d161c868acb7c1ecd1e4
