配置文件语法可否备注一下？

文档链接：[配置加载流程](http://dubbo.apache.org/zh-cn/docs/user/configuration/configuration-load-process.html)

原文中
```
dubbo.application.parameters.item1=value1
dubbo.application.parameters.item2=value2
```
会绑定到 `ApplicationConfig`的`Map`中。

然而，个人在测试时遇到`spring-beans: 5.2.2.RELEASE`中，基于此语法无法成功绑定，正确的语法：
```
dubbo.application.parameters[item1]=value1
dubbo.application.parameters[item2]=value2
```

Start with the linked 配置加载流程 documentation page and locate the example using dubbo.application.parameters.item1 and item2. Document the bracketed syntax shown in the issue, including the binding context described for spring-beans 5.2.2.RELEASE, then verify the rendered page preserves both configuration examples correctly.

Written by the indexing model from the issue text.