Document System.Text.Json.JsonDocument (#2907)

* Document System.Text.Json.JsonDocument

* fixed bad cref

Author: carlossanlop

xml/System.Text.Json/JsonDocument.xml

@@ -48,7 +48,7 @@ This class utilizes resources from pooled memory to minimize the impact of the g
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
+        <summary>Releases the resources used by this <see cref="T:System.Text.Json.JsonDocument" /> instance.</summary>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -322,7 +322,7 @@ This method makes a copy of the data the reader acted on, so there is no caller
       </ReturnValue>
       <Docs>
         <summary>Gets the root element of this JSON document.</summary>
-        <value>To be added.</value>
+        <value>A <see cref="T:System.Text.Json.JsonElement" /> representing the value of the document.</value>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -372,4 +372,4 @@ This method makes a copy of the data the reader acted on, so there is no caller
       </Docs>
     </Member>
   </Members>
-</Type>
+</Type>