bump to 3.7.0

CHANGELOG.md

-# Unreleased
+# 3.7.0
 * Fix #453
 
 # 3.6.1+4

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: 3.6.1+4
+version: 3.7.0
 homepage: https://github.com/JarvanMo/fluwx
 
 environment: