Update "What's new in ASP.NET Core in .NET 11" for Preview 3 (#36991)

* Initial plan

* Add What's New include files for ASP.NET Core .NET 11 Preview 3

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Co-authored-by: wadepickett <10985336+wadepickett@users.noreply.github.com>

* Apply suggestion from @wadepickett

* Rename preview3 include files to preview-3 to fix build warnings

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* Apply suggestion from @wadepickett

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: wadepickett <10985336+wadepickett@users.noreply.github.com>
Co-authored-by: Wade Pickett <wpickett@microsoft.com>

Author: Copilot

aspnetcore/release-notes/aspnetcore-11.md

@@ -62,6 +62,10 @@ This section describes miscellaneous new features in .NET 11.
 
 [!INCLUDE[](~/release-notes/aspnetcore-11/includes/performance-improvements-preview2.md)]
 
+[!INCLUDE[](~/release-notes/aspnetcore-11/includes/zstandard-compression-preview-3.md)]
+
+[!INCLUDE[](~/release-notes/aspnetcore-11/includes/http3-early-request-processing-preview-3.md)]
+
 ## Breaking changes
 
 Use the articles in [Breaking changes in .NET](/dotnet/core/compatibility/breaking-changes) to find breaking changes that might apply when upgrading an app to a newer version of .NET.

aspnetcore/release-notes/aspnetcore-11/includes/http3-early-request-processing-preview-3.md

@@ -0,0 +1,3 @@
+### HTTP/3 starts processing requests earlier
+
+Kestrel now starts processing HTTP/3 requests without waiting for the control stream and SETTINGS frame first, which reduces first-request latency on new connections.

aspnetcore/release-notes/aspnetcore-11/includes/zstandard-compression-preview-3.md

@@ -0,0 +1,19 @@
+### Zstandard response compression and request decompression
+
+ASP.NET Core now supports [Zstandard (zstd)](https://facebook.github.io/zstd/) for both response compression and request decompression. This adds zstd support to the existing response-compression and request-decompression middleware and enables zstd by default.
+
+```csharp
+var builder = WebApplication.CreateBuilder(args);
+
+builder.Services.AddResponseCompression();
+builder.Services.AddRequestDecompression();
+builder.Services.Configure<ZstandardCompressionProviderOptions>(options =>
+{
+    options.CompressionOptions = new ZstandardCompressionOptions
+    {
+        Quality = 6 // 1-22, higher = better compression, slower
+    };
+});
+```
+
+Thank you [@manandre](https://github.com/manandre) for this contribution!