add README

Signed-off-by: Xinyu Ge <xinyu.ge@zilliz.com>

README.md

@@ -78,7 +78,7 @@ and a corresponding vector in numpy.ndarray given a video input data.
 ​	Input video data using local path in string or video frames in ndarray.
 
 
-**Returns**: *(list, list)*
+**Returns**: *(list, list, Tensor)*
 
-​	A tuple of (labels, scores),
+​	A tuple of (labels, scores, features),
 which contains lists of predicted class names and corresponding scores.