Automatically port System.Text.Json.JsonSerializerOptions (dotnet#3015)

* Automatically port System.Text.Json.JsonSerializerOptions

* edits

Author: carlossanlop

xml/System.Text.Json/JsonSerializerOptions.xml

@@ -175,8 +175,8 @@ It is not used when deserializing.
         <ReturnType>System.Text.Encodings.Web.JavaScriptEncoder</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>To be added.</summary>
-        <value>To be added.</value>
+        <summary>Gets or sets the encoder to use when escaping strings, or <see langword="null" /> to use the default encoder.</summary>
+        <value>The JavaScript character encoding.</value>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>