* [Refactor] Refactor the rest data transforms and fix some docstring.
* Use `mmengine` instead of `mmcv`
* Refactor KFold dataset tools
* Fix docstring according to comments
* Add Res2Net from mmdet, and change it to mmcls style.
* Align structure with official repo
* Support `deep_stem` and `avg_down` option
* Add Res2Net configs
* Add metafile&README and update model zoo
* Add unit tests
* Imporve docstring.
* Improve according to comments.