[Refactoring] Replace Newtonsoft.Json with System.Text.Json

[AlleSchonWeg]

Description

Replace Newtonsoft.Json with System.Text.Json and use

Background & Context

Newtonsoft.Json is old and have problems with trimming/aot.
More info: https://learn.microsoft.com/en-us/dotnet/maui/deployment/nativeaot?view=net-maui-9.0#adapt-an-app-to-native-aot-deployment

This will help to make the library more AOT/trimmer friendly.

Screenshots, Attachments, Links

[thomasgalliker]

Valid point. Just not much time available.