Added targets for net6.0 and net8.0 and allow RollForward

[FroggieFrog]

Description:

Fixes #447
Fixes #495

This PR adds the TargetFrameworks net6.0 and net8.0.
Also as sugegsted in #419 the RollForward property was added.

I'm not sure about the piepline configurations, but adjusted them according to #419

Checklist:

• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested my changes by running the extension in VS2017
• I have tested my changes by running the extension in VS2019
• I have tested my changes by running the extension in VS2022
• If changes to the documentation are needed, I have noted this in the description above

[renebentes]

Any update on this? I would really like to use it without installing .NET 6

[Jeanjean]

Me too