SpriterDotNet NuGet packages broken in latest release of MonoGame.

[BrainSlugs83]

Reproduction Steps:

1.) Create a new MonoGame project (Desktop, or GL).
2.) Build & Run the project, observe that it works, and you see the iconic cornflower blue MonoGame window.
3.) Close the app, and return to Visual Studio.
4.) Add the Spriter.MonoGame NuGet package.
5.) Build & Run the project, observe that it crashes in the constructor on the line that reads Content.RootDirectory = "Content"; with a NullReferenceException, and that the Content object is null.

[loodakrawa]

Hey, thanks for reporting. MonoGame content pipeline is causing so much grief. I'll plan to handle it differently in the next version.