Add `frameworkReference`

Description

Is it possible to include frameworkReferences (e.g. to Microsoft.AspNetCore.App) when packing an application?
I'm creating a library that internally starts a self-hosted ASP.NET core server. With .NET Core 3 it seems you either should use Microsoft.NET.Sdk.Web or add a frameworkReference to Microsoft.AspNetCore.App (either in the project file or in the .nuspec file). dotnet pack doesn't work when using Microsoft.NET.Sdk.Web (disables packaging), but dotnet packing is possible when using frameworkReference (the information is included in the .nupkg). However Paket doesn't include any information about frameworkReferences when packing the library.

Repro steps

1. Create a new project and replace *.fsproj with the following:

   <Project Sdk="Microsoft.NET.Sdk">
   
   <PropertyGroup>
     <TargetFramework>netcoreapp3.0</TargetFramework>
     <OutputType>dll</OutputType>
   </PropertyGroup>
   
   <ItemGroup>
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
   </ItemGroup>
   
   <ItemGroup>
     <Compile Include="Program.fs" />
   </ItemGroup>
   
   <Import Project=".paket\Paket.Restore.targets" />
   </Project>
   

2. Pack the application with dotnet pack and paket pack

3. Open the package with Nuget Package Explorer and find that dotnet pack includes the frameworkReference and paket pack does not.

Start with the supplied project file and its .paket\Paket.Restore.targets import, then reproduce the difference between dotnet pack and paket pack. Inspect the generated packages and use the listed FrameworkReference entry as the expected input; done means Paket's package includes the corresponding frameworkReference information.