bump to 4.5.6

CHANGELOG.md

+# 4.5.6
+* Merge #639
+
 # 4.5.5
 * iOS 最小版本支持为12.0
 

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: 4.5.5
+version: 4.5.6
 homepage: https://github.com/OpenFlutter/fluwx
 
 environment: