Better NuGet support

[nasser]

Right now pulling packages off of NuGet is quite primitive and just shells out to the nuget CLI utility. This makes it difficult to specify e.g. what target framework to download packages for. Ideally nostrand would use NuGet's C# API internally for full control. That API seems like a beast, though

https://daveaglick.com/posts/exploring-the-nuget-v3-libraries-part-1 https://daveaglick.com/posts/exploring-the-nuget-v3-libraries-part-2 https://daveaglick.com/posts/exploring-the-nuget-v3-libraries-part-3