* support bf16 in AmpOptimWrapper

* add docstring

* modify docs

* add unittests for bf16 in AmpOptimWrapper

* fix type

* fix to pass ci

* fix ut skip logic to pass ci

* fix as comment

* add type hints

* fix docstring and add warning information

* remove check for pytorch>=1.6 in unittest

* modify unittest

* modify unittest

* remove torch.float32 && torch.float64 from valid dtypes

* fix as comments

* minor refine docstring

* fix unittest parameterized to pass CI

* fix unittest && add back torch.float32, torch.float64

* [Docs] Move examples to a new directory

* fix typo

* [Docs] Translate examples docs

* Update docs/en/examples/resume_training.md

Co-authored-by: Qian Zhao <112053249+C1rN09@users.noreply.github.com>

Co-authored-by: Qian Zhao <112053249+C1rN09@users.noreply.github.com>

* [WIP] Refactor-docs-structure

* [Docs] Check link and fix rst  (#498)

* check link

* fix rst

* Fix conf.py

* Fix lint

* minor refine

* minor refine

* modify zh_readme and index.rst

* add migration exampls get_started design to en

* add tutorials to en

* correct chinese doc link

* Apply suggestions from code review

* Update docs/en/advanced_tutorials/distributed.md

Co-authored-by: Zaida Zhou <58739961+zhouzaida@users.noreply.github.com>

Co-authored-by: Mashiro <57566630+HAOCHENYE@users.noreply.github.com>