How to create a library targeting ASP.NET Core 3.0

**Help us make content visible**

- How to build a library targeting ASP.NET Core

**Describe the new topic**

Since the WebSDK has an implicit framework reference to AspNetCore, most folks don't see `<FrameworkReferences>` at all. We need some guidance for library authors on how to target ASP.NET. We probably need to include guidance on when to multi-target as well.
