bump to 5.5.4

CHANGELOG.md

+# 5.5.4
+* 分享到小程序时，增加scene字段，尽管微信只支持分享小程序到会话.
+
 # 5.5.3
 * Fix [#706](https://github.com/OpenFlutter/fluwx/issues/706)
 

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: 5.5.3
+version: 5.5.4
 homepage: https://github.com/OpenFlutter/fluwx
 
 environment: