Mark SkipValidationAttribute as Experimental

Author: oroztocil

src/Validation/src/SkipValidationAttribute.cs

@@ -1,13 +1,16 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Diagnostics.CodeAnalysis;
+
 namespace Microsoft.Extensions.Validation;
 
 /// <summary>
 /// Indicates that an object property should be skipped for validation.
 /// The generator will not generate validation code for this property and its type.
 /// </summary>
 [AttributeUsage(AttributeTargets.Class | AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.Field)]
+[Experimental("ASP0029", UrlFormat = "https://aka.ms/aspnet/analyzer/{0}")]
 public sealed class SkipValidationAttribute : Attribute
 {
 }