NUnit4 support

[louisnayegon]

I have noticed in your test code you are still using version 3 of NUnit

Reqnroll/Plugins/Reqnroll.NUnit.ReqnrollPlugin/Reqnroll.NUnit.ReqnrollPlugin.csproj

Line 10 in 574d738

<PackageReference Include="NUnit" Version="3.13.1" />

Does this work with v4?
If not when do you expect to support this?

[ajeckmans]

We just came out of a period where updates were lacking. If it is possible to support v3 and v4 then we can easily do this, and we would welcome any PR for it.

[gasparnagy]

Does this work with v4?

@louisnayegon It is also a help for us if you try and see if you encounter any problems.