NET8 support

[iRubens]

Hi @ektrah ,
as you're probably aware last year NET8 was released.

Being a LTS release with a lot of performance improvements it would be nice to support it directly.

I've tried to add the support for it, tests are ok on NET 6, 7 and 8.

[ektrah]

Thanks for your contribution!

As you probably know, there is no problem using an assembly compiled for net6.0 in a project that targets net8.0. You only need assemblies compiled for multiple frameworks if there are actually differences between those assemblies, e.g., if you use #if NET8_0_OR_GREATER or similar.

NSec doesn't have any #ifs. So, unless there are significant compiler changes that generate different assembles for net6.0 and net8.0, I think compiling for both net6.0 and net8.0 just doubles the size of the NuGet package. I'd prefer not to do that, tbh.

Thanks for updating the tests, though. That's overdue. May I ask you to also update the GH Actions workflow while you're at it?

[iRubens]

Haha TIL about "forward" support for >NET6 projects. I reverted the projects to single NET6 target.
I also tried to update the actions to reflect the NET8 support (supposing they work like DevOps' pipelines).
I'm hoping it'll work nicely.

[ektrah]

Thanks a lot!