v3 readme

Author: 李卓原

README.md

@@ -16,8 +16,8 @@
 [Update log](https://github.com/OpenFlutter/flutter_screenutil/blob/master/CHANGELOG.md)
 
 ## Note
-v3 requires `flutter >= 1.19.0`. 
-v2 for current stable version of flutter.
+[v3](https://github.com/OpenFlutter/flutter_screenutil/tree/beta) requires `flutter >= 1.19.0`.
+[v2](https://github.com/OpenFlutter/flutter_screenutil) for current stable version of flutter.
 
 ## Usage:
 

README_CN.md

@@ -20,8 +20,8 @@
 [更新日志](https://github.com/OpenFlutter/flutter_screenutil/blob/master/CHANGELOG.md)
 
 ## Note
-v3可用于`flutter> = 1.19.0`
-v2用于当前Flutter的`stable`版本。
+[v3](https://github.com/OpenFlutter/flutter_screenutil/tree/beta)可用于`flutter> = 1.19.0`
+[v2](https://github.com/OpenFlutter/flutter_screenutil)用于当前Flutter的`stable`版本。
 
 ## 使用方法:
 

README_PT.md

@@ -16,8 +16,8 @@
 [Histórico de atualizações](https://github.com/OpenFlutter/flutter_screenutil/blob/master/CHANGELOG.md)
 
 ## Note
-v3 requer `flutter> = 1.19.0`.
-v2 é usado para a versão atual de flutter estável.
+[v3](https://github.com/OpenFlutter/flutter_screenutil/tree/beta) requer `flutter> = 1.19.0`.
+[v2](https://github.com/OpenFlutter/flutter_screenutil) é usado para a versão atual de flutter estável.
 
 ## Como usar: