Add tts python example and change onnx to paddle (#420)

* add tts example

* update example

* update use fd engine

* add tts python example

* add readme

* fix comment

* change paddle model

* fix readme style

Co-authored-by: Jason <jiangjiajun@baidu.com>

examples/audio/pp-tts/python/README.md

@@ -0,0 +1,27 @@
+([简体中文](./README_cn.md)|English)
+
+# PP-TTS Streaming Text-to-Speech Python Example
+
+## Introduction
+This demo is an implementation of starting the streaming speech synthesis.
+
+## Usage
+
+### 1. Installation
+```bash
+apt-get install libsndfile1 wget zip
+For Centos, yum install libsndfile-devel wget zip
+python3 -m pip install --upgrade pip
+pip3 install -U fastdeploy-python -f https://www.paddlepaddle.org.cn/whl/fastdeploy.html
+pip3 install -U paddlespeech paddlepaddle soundfile matplotlib
+```
+
+### 2. Run the example
+```bash
+python3 stream_play_tts.py
+```
+
+### 3. Result
+The complete voice synthesis audio is saved as `demo_stream.wav`.
+
+User can install `pyaudio` on their own terminals to play the results of speech synthesis in real time. The relevant code is in `stream_play_tts.py` and you can debug and run it yourself.