Add a note about alterations and ifdef to polyfill

Author: SeeminglyScience

src/PowerShellEditorServices/Index.cs

@@ -1,6 +1,10 @@
 // <auto-generated>
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
+// (with alterations)
+#if NET5_0_OR_GREATER
+[assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.Index))]
+#else
 
 using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
@@ -152,3 +156,4 @@ public static void ThrowValueArgumentOutOfRange_NeedNonNegNumException()
         }
     }
 }
+#endif

src/PowerShellEditorServices/Range.cs

@@ -1,6 +1,10 @@
 // <auto-generated>
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
+// (with alterations)
+#if NET5_0_OR_GREATER
+[assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.Range))]
+#else
 
 global using Range = OmniSharp.Extensions.LanguageServer.Protocol.Models.Range;
 
@@ -116,3 +120,4 @@ public static void ThrowArgumentOutOfRangeException(string parameterName)
         }
     }
 }
+#endif