Add specific link to code copied from ASP.NET Core and System.Text.Json

Author: DustinCampbell

src/Shared/Microsoft.AspNetCore.Razor.Utilities.Shared/PooledArrayBufferWriter`1.cs

@@ -1,7 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the MIT license. See License.txt in the project root for license information.
 
-// Copied from https://github.com/dotnet/runtime
+// Copied from https://github.com/dotnet/aspnetcore/blob/207bc7d00c00bf454dc83789d6824609b1d8b02a/src/Shared/PooledArrayBufferWriter.cs,
+// which is derived from https://github.com/dotnet/runtime/blob/abb5c348f242e546b5768ad70ebe4051f08f7d24/src/libraries/Common/src/System/Text/Json/PooledByteBufferWriter.cs
 
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;