Update 22-to-30.md (#17844)

* Update 22-to-30.md

* Update 22-to-30.md

* Update aspnetcore/migration/22-to-30.md

Co-Authored-By: Scott Addie <10702007+scottaddie@users.noreply.github.com>

Co-authored-by: Scott Addie <10702007+scottaddie@users.noreply.github.com>

Author: Rick-Anderson

aspnetcore/migration/22-to-30.md

@@ -12,7 +12,10 @@ uid: migration/22-to-30
 
 By [Scott Addie](https://github.com/scottaddie) and [Rick Anderson](https://twitter.com/RickAndMSFT)
 
-This article explains how to update an existing ASP.NET Core 2.2 project to ASP.NET Core 3.0.
+This article explains how to update an existing ASP.NET Core 2.2 project to ASP.NET Core 3.0. It might be helpful to create a new ASP.NET Core 3.0 project to:
+
+* Compare with the ASP.NET Core 2.2 code.
+* Copy the relevant changes to your ASP.NET Core 3.0 project.
 
 ## Prerequisites