Update README.md
Summary:
Add a Few-Shot Object Detection project link builts on top of detectron2.
Pull Request resolved:
@@ -35,3 +35,4 @@ External projects in the community that use detectron2:
+ [CenterMask](https://github.com/youngwanLEE/centermask2)
+ [Res2Net backbones](https://github.com/Res2Net/Res2Net-detectron2)
+ [VoVNet backbones](https://github.com/youngwanLEE/vovnet-detectron2)
++ [FsDet](https://github.com/ucbdrive/few-shot-object-detection), Few-Shot Object Detection.
