[handpose] Update README. (tensorflow#428)

Author: annxingyuan

handpose/README.md

@@ -1,7 +1,7 @@
 # MediaPipe Handpose
 Note: this model can only detect a maximum of one hand in the input - multi-hand detection is coming in a future release.
 
-MediaPipe Handpose is a lightweight ML pipeline consisting of two models: A palm detector and a hand-skeleton finger tracking model. It predicts 21 2D hand keypoints per detected hand. For more details, please read our Google AI [blogpost](https://ai.googleblog.com/2019/08/on-device-real-time-hand-tracking-with.html).
+MediaPipe Handpose is a lightweight ML pipeline consisting of two models: A palm detector and a hand-skeleton finger tracking model. It predicts 21 3D hand keypoints per detected hand. For more details, please read our Google AI [blogpost](https://ai.googleblog.com/2019/08/on-device-real-time-hand-tracking-with.html).
 
 <img src="demo/demo.gif" alt="demo" style="width:640px" />