Link to System.Text.Json overview (#3306)

Author: tdykstra

xml/System.Runtime.Serialization.Json/DataContractJsonSerializer.xml

@@ -40,8 +40,10 @@
     <remarks>
       <format type="text/markdown"><![CDATA[  
   
-## Remarks  
- Use the <xref:System.Runtime.Serialization.Json.DataContractJsonSerializer> class to serialize instances of a type into a JSON document and to deserialize a JSON document into an instance of a type. For example, you can create a type named `Person` with properties that contain essential data, such as a name and address. You can then create and manipulate an instance of the `Person` class and write all of its property values in a JSON document for later retrieval. This JSON document can later be deserialized into the `Person` class or another class with an equivalent data contract.  
+## Remarks 
+ For most scenarios that involve serializing to JSON and deserializing from JSON, we recommend the [tools in the System.Text.Json namespace](/dotnet/standard/serialization/system-text-json-overview). 
+ 
+ If your scenario requires the <xref:System.Runtime.Serialization.Json.DataContractJsonSerializer> class, you can use it to serialize instances of a type into a JSON document and to deserialize a JSON document into an instance of a type. For example, you can create a type named `Person` with properties that contain essential data, such as a name and address. You can then create and manipulate an instance of the `Person` class and write all of its property values in a JSON document for later retrieval. This JSON document can later be deserialized into the `Person` class or another class with an equivalent data contract.  
   
  If an error occurs during the serialization of an outgoing reply on the server or the reply operation throws an exception for some other reason, it may not get returned to the client as a fault.