Modelzoo updates

## 🚀 Feature
I'm an enthusiastic user of D2, compared with others sw it's more easy, complete, and extensible to use.
I have just one question: it seems that modelzoo is not so much updated, compared with other libraries available for ML CV.
At the moment the model with best box AP=44.3, is cascade_mask_rcnn_R_50_FPN_3x, even if it's almost 2 years old.
Can you please publish some model from recent papers?
Now other frameworks offers models to retrain with AP over 50.
Thanks

## Motivation & Examples
I achieved very good results in object detection, using even TTA and other parameters optimization (NMS_THRESH_TEST, PRE_NMS_TOPK_TEST, ...). I would like to try some other models, from recent papers.