fix all bug in infer.py for multi class

fix a bug for multi class

add ppyoloe_crn_l

add square brackets for im_scale_factor

add retinanet inference model

add picodet three model

update readme.txt

Update readme.md

Update readme.md

update for \n

update for new line

update for format

Update readme.md

update readme.md format

update readme.txt format