Add a new route to sample app that display OS and .NET versions (#41901)

* Add a new route to sample app that display OS and .NET versions

* Apply suggestions from code review

Co-authored-by: Stephen Halter <halter73@gmail.com>

Co-authored-by: Bethel Arthur <t-barthur@microsoft.com>
Co-authored-by: Stephen Halter <halter73@gmail.com>

Author: 3 people

src/Http/samples/MinimalSample/Program.cs

@@ -16,6 +16,14 @@
 string Plaintext() => "Hello, World!";
 app.MapGet("/plaintext", Plaintext);
 
+var message =
+    $"""
+    Operating System: {Environment.OSVersion}
+    .NET version: {Environment.Version}
+    """;
+
+app.MapGet("/", () => message);
+
 var nestedGroup = app.MapGroup("/group/{groupName}")
    .MapGroup("/nested/{nestedName}")
    .WithMetadata(new TagsAttribute("nested"));