【Hackathon 8th No.7】Add hints for installing with -e (#3979)

* Update README_cn.md

* Update README.md

Author: Liyulingyue

README.md

@@ -265,6 +265,8 @@ git clone https://github.com/PaddlePaddle/PaddleSpeech.git
 cd PaddleSpeech
 pip install pytest-runner
 pip install .
+# If you need to install in editable mode, you need to use --use-pep517. The command is as follows:
+# pip install -e . --use-pep517
 ```
 
 For more installation problems, such as conda environment, librosa-dependent, gcc problems, kaldi installation, etc., you can refer to this [installation document](./docs/source/install.md). If you encounter problems during installation, you can leave a message on [#2150](https://github.com/PaddlePaddle/PaddleSpeech/issues/2150) and find related problems

README_cn.md

@@ -272,6 +272,8 @@ git clone https://github.com/PaddlePaddle/PaddleSpeech.git
 cd PaddleSpeech
 pip install pytest-runner
 pip install .
+# 如果需要在可编辑模式下安装，需要使用 --use-pep517，命令如下
+# pip install -e . --use-pep517
 ```
 
 更多关于安装问题，如 conda 环境，librosa 依赖的系统库，gcc 环境问题，kaldi 安装等，可以参考这篇[安装文档](docs/source/install_cn.md)，如安装上遇到问题可以在 [#2150](https://github.com/PaddlePaddle/PaddleSpeech/issues/2150) 上留言以及查找相关问题