Rename README.zh-CN.md to README.zh-CN.MD

Extensions/FreeSql.Extensions.JsonMap/README.zh-CN.MD

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+**中文** | [English](README.MD)
+
+FreeSql 扩展包，将值对象映射成 `typeof(string)`，安装扩展包：
+
+> dotnet add package FreeSql.Extensions.JsonMap
+
+```csharp
+fsql.UseJsonMap(); //开启功能
+
+class TestConfig
+{
+    public int clicks { get; set; }
+    public string title { get; set; }
+}
+
+[Table(Name = "sysconfig")]
+public class S_SysConfig<T>
+{
+    [Column(IsPrimary = true)]
+    public string Name { get; set; }
+
+    [JsonMap]
+    public T Config { get; set; }
+}
+```