Run and report on code coverage on build

[baynezy]

• https://github.com/OpenCover/opencover
• https://github.com/codecov/example-csharp
• https://codecov.io/

[baynezy]

Looks like OpenCover does not have .Net Core support yet.
OpenCover/opencover#601

[baynezy]

Look at https://github.com/tonerdo/coverlet

[baynezy]

Currently blocked by codecov/codecov-exe#30