Azure Pipelines build and release pipeline

At present, we have a mix of build systems that I would like to unify.

1. Azure Pipelines for Linux, Windows and macOS.
2. Travis for Linux and macOS
3. Appveyor for Windows

I'd like to standardize around Azure Pipelines. At the moment, it's only doing a build for validation. I would like the build step to:

1. Create a nuget package (see AppVeyor's build configuration)
2. Upload that nuget package to Azure Artifacts

Then I'd like to have a separate release pipeline that will:

1. Take the nuget package from Azure Artifacts
2. Upload the nuget package to nuget.org

Comienza con la compilación de validación existente de Azure Pipelines y la configuración de compilación de AppVeyor, que son los puntos de entrada indicados en el issue. Sigue cómo se crea el paquete NuGet e identifica los pasos de publicación en Azure Artifacts y nuget.org. Se considera terminado cuando Azure Pipelines compila y almacena el paquete, mientras que un pipeline de release independiente lo publica en nuget.org.