Add missing docstrings for ONNX converter API. Fixes #67393 (#67640) (#68489)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/68489
Test Plan: Imported from OSS
Reviewed By: jansel
Differential Revision: D32483783
Pulled By: msaroufim
fbshipit-source-id: 512e4495040a6a9833d501de2301f1709b0352b9
