Expose IHelpBuilder via the InvocationContext

Author: Keboo

src/System.CommandLine/Invocation/InvocationContext.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using System.CommandLine.Binding;
+using System.CommandLine.Help;
 using System.CommandLine.Parsing;
 using System.Threading;
 
@@ -27,6 +28,8 @@ public InvocationContext(
 
         public Parser Parser => BindingContext.ParseResult.Parser;
 
+        public IHelpBuilder HelpBuilder => Parser.Configuration.HelpBuilderFactory(BindingContext);
+
         public Resources Resources => Parser.Configuration.Resources;
 
         public ParseResult ParseResult