Add object_detection to the main README
Add object_detection to the main README

tombstone/models,alexgorban/models,xcyan/models,cshallue/models,sshleifer/object_detection_kitti,jiaphuan/models,cshallue/models,derekjchow/models,alexgorban/models,jch1/models,tombstone/models,derekjchow/models,alexgorban/models,tombstone/models,cshallue/models,sshleifer/object_detection_kitti,sshleifer/object_detection_kitti,jiaphuan/models,jiaphuan/models,jazcollins/models,jiaphuan/models,xcyan/models,jch1/models,jazcollins/models,jch1/models,cshallue/models,tombstone/models,tombstone/models,jch1/models,sshleifer/object_detection_kitti,jazcollins/models,jiaphuan/models,derekjchow/models,xcyan/models,xcyan/models,sshleifer/object_detection_kitti,alexgorban/models,alexgorban/models,jch1/models,jiaphuan/models,tombstone/models,jazcollins/models,jazcollins/models,sshleifer/object_detection_kitti,xcyan/models,xcyan/models,derekjchow/models,cshallue/models,jch1/models,zbigniewwojna/text-rcnn,derekjchow/models,jazcollins/models