Support .Net 6

[Meir017]

Let's add support for .Net 6 as well

[jnyrup]

Out of curiosity, what's the benefit of the additional target?
The downside is an increase in size of nupkg.

[Corniel]

@Meir017 seems to work now. Although I don't understand why. My own analyzer (https://www.nuget.org/packages/Qowaiv.Analyzers.CSharp) nor Sonar.Analyzer.CSharp have a .NET 6 target, but lack the issue.