Remove System.text.Json dependency from net 6+

[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 directly by the framework.

Describe alternatives you've considered
Accept the additional dependency

Additional context
n/a