* New LetterBox transform

YOLOv5 LetterBox class for image preprocessing, i.e. T.Compose([T.ToTensor(), LetterBox(size)])
Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>

* Update augmentations.py
Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>

* Update augmentations.py
Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>

* Update augmentations.py
Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* cleanup

* cleanup

* cleanup

* cleanup

* cleanup
Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>