Document C# union types in ASP.NET Core (.NET 11) - #37261

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v3, dotnet/docs-actions/actions/status-checker@main. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/