bump to 5.0.0

CHANGELOG.md

+# 5.0.0
+* 使用了多端统一API，详情请点击[这里](https://developers.weixin.qq.com/doc/oplatform/Mobile_App/Share_and_Favorites/Android.html)
+* 分享时所有的缩略图请使用`thumbData`字段
+* Fluwx不会再对任何图片进行压缩处理
+
 # 4.6.0
 * Android SDK => 6.8.30
 * 分享新增基础字段:thumbData

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: 4.6.0
+version: 5.0.0
 homepage: https://github.com/OpenFlutter/fluwx
 
 environment: