.NET 6 enablement

[Luke]

I'll take a look at submitting something but this should probably be bumped to .NET 6 (and possibly left there until the next LTS). I think there's a way to target both 5 and 6 in a single project, which would probably be ideal.

[Nate McMaster]

The project already compiles for .NET 6 #103, so I don't think there is any action item here.