Update README (#572)

 # Introduction
 
-Documentation: <https://k2-fsa.github.io/sherpa/onnx/index.html>
+This repository supports running the following functions **locally**
 
-See <https://github.com/k2-fsa/sherpa>
+  - Speech-to-text (i.e., ASR)
+  - Text-to-speech (i.e., TTS)
+  - Speaker identification
 
-This repo uses [onnxruntime](https://github.com/microsoft/onnxruntime) and
-does not depend on libtorch.
+on the following platforms and operating systems:
+
+  - Linux, macOS, Windows
+  - Android
+  - iOS
+  - Raspberry Pi
+  - etc
+
+# Useful links
+
+- Documentation: https://k2-fsa.github.io/sherpa/onnx/
+- APK for the text-to-speech engine: https://k2-fsa.github.io/sherpa/onnx/tts/apk-engine.html
+- APK for speaker identification: https://k2-fsa.github.io/sherpa/onnx/speaker-identification/apk.html
+
+# How to reach us
+
+Please see
+https://k2-fsa.github.io/sherpa/social-groups.html
+for 新一代 Kaldi **微信交流群** and **QQ 交流群**.