Add documentation for System.Diagnostics.ProcessStartInfo.StandardInputEncoding (#3227)

* Add documentation for System.Diagnostics.ProcessStartInfo.StandardInputEncoding

* remove attributes

* formatting change

Author: wtgodbe

xml/System.Diagnostics/ProcessStartInfo.xml

@@ -1341,9 +1341,16 @@ You can use asynchronous read operations to avoid these dependencies and their d
         <ReturnType>System.Text.Encoding</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>To be added.</summary>
-        <value>To be added.</value>
-        <remarks>To be added.</remarks>
+        <summary>Gets or sets the preferred encoding for standard input.</summary>
+        <value>An object that represents the preferred encoding for standard input. The default is <see langword="null" />.</value>
+        <remarks>
+          <format type="text/markdown"><![CDATA[  
+  
+## Remarks  
+ If the value of the `StandardInputEncoding` property is `null`, the process uses the default standard input encoding for the standard input. The `StandardInputEncoding` property must be set before the process is started. Setting this property does not guarantee that the process will use the specified encoding. The application should be tested to determine which encodings the process supports.  
+  
+ ]]></format>
+        </remarks>
       </Docs>
     </Member>
     <Member MemberName="StandardOutputEncoding">