Replace Newtonsoft.Json with System.Text.Json

Removed the Newtonsoft.Json dependency in favor of System.Text.Json in the 'TypeExtensions' class and accordingly updated the .csproj file. The 'ConvertObjectToJson' method has been updated to use the new JSON handling library, with an option for custom JsonSerializerOptions.

net 8

fixed namespace

Added FluentReactiveWindow.cs

ver

skiaimage fixes

Avalonia 10 downgrade

ability to enable and disable rounded corners

Update to Avalonia 11

nuget