Improve dependency handling

[thompson-tomo]

Is your feature request related to a problem? Please describe.
I want to minimise dependencies in my project by utilising framework dependencies wherever possible

Describe the solution you'd like
I want the package to not have an explicit dependency on System.Text.Json as it can be provided by the framework when targeting net 6.

Describe alternatives you've considered
Accept the additional dependency

Additional context
n/a

[dbrattli]

I'm not sure I understand. The package do not have an explicit depencency on System.Text.Json:

[dbrattli]

Ok, I think I understand this. You want the Oryx.SystemTextJson to be built for net6 (and probably net8) without the direct dependency on System.Text.Json? Not sure how we can make it a conditional dependency based on framework.