Update README.md

Author: zhangMonday

README.md

@@ -1,5 +1,5 @@
 # m4a_to_mp3
-将文件夹下的所有m4a文件转换为mp3格式（包括其子文件夹）。Convert all m4a files under the folder (including its subfolders) to mp3 format 
+将文件夹下的所有m4a文件替换为mp3格式（包括其子文件夹）。Convert all m4a files under the folder (including its subfolders) to mp3 format 
 
 在使用前，你需要在源代码中修改需要转换的文件夹地址，并且下载ffmpeg库
 Before using it, you need to modify the folder address to be converted in the source code and download the ffmpeg library