Separate the dependency on AspNetCore

[d2dyno1]

To allow for more flexibility the AspNetCore dependency (Sdk="Microsoft.NET.Sdk.Web" in the project file) should be moved ideally to a separate NuGet package. Platforms like Blazor WASM Android, iOS (and by extension MacCatalyst) cannot be built with a dependency on AspNetCore

[ramondeklein]

The previous (non .NET core) version of this library used different packages, because a lot of different HTTP methods were available (HttpListener, ASP.NET, Kestrel), but Kestrel has been the defacto standard for .NET Core. Supporting other platforms hasn't been a goal for this library. It was intended to be used in traditional .NET Core environments.

As I'm not doing any .NET Core development for the past 6 months, I don't think I will have the time to implement this. Feel free to fork or submit a PR that implements this and I'll see if I can migrate it.