docs: update uniapp config (#249)

Author: lgz5689

docs/guides/solution/offlinePush.mdx

@@ -43,4 +43,5 @@ enable: #选择 getui 或者 fcm
 **Flutter 客户端** 的详细接入方式可参考下方链接：
 - [OpenIM Flutter Demo 配置说明](https://github.com/openimsdk/openim-flutter-demo/blob/main/CONFIGKEY.zh-CN.md)
 - [OpenIM iOS Demo 配置说明](https://github.com/openimsdk/openim-ios-demo/blob/main/CONFIGKEY.zh-CN.md)
+- [OpenIM Uniapp Demo 配置说明](https://github.com/openimsdk/open-im-uniapp-demo/blob/main/CONFIGKEY.md)