Jst/add yolov5 example

[Jiang-Stan]

Model	qconfig	mAP50-95	mAP50	prec	recall
YOLOv5n	float	27.7%	45.6%	57.5%	43.2%
YOLOv5n	8w8f	27.2%	45.2%	58.1%	42.6%
YOLOv5s	float	37.1%	56.6%	66.8%	52.1%
YOLOv5s	8w8f	36.8%	56.4%	66.8%	52.0%