Migration from Spline.Core

The package, project, and public namespace were simplified from Spline.Core to Spline.

What changed

NuGet package ID changed from Spline.Core to Spline
project path changed from src/Spline.Core/Spline.Core.csproj to src/Spline/Spline.csproj
public namespace changed from Spline.Core to Spline
solution and workflow references were updated to the new project path

What stayed the same

sample app name: DemoSpline
repository name: Spline

Consumer update checklist

Change package references to Spline.
Change using Spline.Core; to using Spline;.
If you frequently construct the Spline type, add using SplinePath = global::Spline.Spline;.
Update local project references if you consume the source tree directly.
If you have scripts that pack or restore the project by path, update them to src/Spline/Spline.csproj.