Add Containers release notes for .NET 11 Preview 5

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Copilot

release-notes/11.0/preview/preview5/containers.md

@@ -0,0 +1,12 @@
+# Containers in .NET 11 Preview 5 - Release Notes
+
+<!--
+The .NET container images ship out of the dotnet/dotnet-docker repo on its own
+cadence. The container team authors this file directly when content is ready.
+Replace this stub with the Preview 5 highlights (image updates, base OS bumps,
+PowerShell version, etc.).
+-->
+
+There are no container release notes for this preview yet. Watch
+[dotnet/dotnet-docker releases](https://github.com/dotnet/dotnet-docker/releases)
+for the Preview 5 image announcement.