This removes support for .NET Core 2.1, .NET Core 3.1, and .NET 5 which are now out of support from Microsoft.
Additionally, now that .NET Core 2.1 is no longer supported, the old System.Text.Json version is no longer needed. This updates System.Text.Json to 8.0.0 which supports .NET 6+ in use here.
This removes support for .NET Core 2.1, .NET Core 3.1, and .NET 5 which are now out of support from Microsoft.
Additionally, now that .NET Core 2.1 is no longer supported, the old System.Text.Json version is no longer needed. This updates System.Text.Json to 8.0.0 which supports .NET 6+ in use here.
Resolves #30