bump to 3.5.1

CHANGELOG.md

+## 3.5.1
+* 自动释放extMsg
+
 ## 3.5.0
 * update compileSdkVersion
 

pubspec.yaml

 name: fluwx
 description: The capability of implementing WeChat SDKs in Flutter. With Fluwx, developers can use WeChatSDK easily, such as sharing, payment, lanuch mini program and etc.
-version: 3.5.0
+version: 3.5.1
 homepage: https://github.com/JarvanMo/fluwx
 
 environment: