Stop publishing NuGet packages

[objorke]

1. Keeping the OxyPlot Xamarin NuGet packages up-to-date requires frequent updates (due to the Xamarin dependencies)
2. To create stable package releases, we should test on all the supported platforms

This is a lot of work and quite time consuming. An alternative could be to recommend everyone using this library to build it themselves, e.g. include the source code in their project as a git submodule or subtree.

[dsyme]

If it is a lot of work and time consuming, why not ask to bring on extra maintainers to this project and also automate the process?

This package is a great package! and deserves a nuget, like most other packages....

[objorke]

Yes, with more maintainers we could avoid this. It seems like we need some people to support each major platform. The Xamarin platform is extra challenging to automate on CI and requires Apple hardware for testing (MacOS, iOS).