Update Mapster.Tool to include .net6.0 as target framework #387

using Mapster;

Console.WriteLine("Hello, World!");

public class A
{
    public string Str { get; set; }
}

public class B
{
    public string Str { get; set; }
}

[Mapper]
public interface IMapper
{
    A Map(B test);
}

public class MyRegister : IRegister
{
    public void Register(TypeAdapterConfig config)
    {
        config.NewConfig<A, B>();
    }
}

Cannot find assembly path: System.Runtime (type=package, version=5.0.11-servicing.21473.8)
Cannot find assembly path: System.Runtime (type=package, version=5.0.11-servicing.21473.8)
Cannot find assembly path: System.Runtime (type=package, version=5.0.11-servicing.21473.8)
Cannot find assembly path: System.Runtime (type=package, version=5.0.11-servicing.21473.8)
Unhandled exception. System.Reflection.ReflectionTypeLoadException: Unable to load one or more of the requested types.
Could not load file or assembly 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.
Could not load file or assembly 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.
Could not load file or assembly 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.
Could not load file or assembly 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.
   at System.Reflection.RuntimeModule.GetTypes(RuntimeModule module)
   at System.Reflection.RuntimeModule.GetTypes()
   at System.Reflection.Assembly.GetTypes()
   at Mapster.TypeAdapterConfig.<>c.<Scan>b__87_0(Assembly assembly) in D:\git\Mapster\src\Mapster\TypeAdapterConfig.cs:line 619
   at System.Linq.Enumerable.SelectArrayIterator`2.MoveNext()
   at System.Linq.Enumerable.SelectManySingleSelectorIterator`2.ToList()
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Mapster.TypeAdapterConfig.Scan(Assembly[] assemblies) in D:\git\Mapster\src\Mapster\TypeAdapterConfig.cs:line 619
   at Mapster.Tool.Program.GenerateMappers(MapperOptions opt) in D:\git\Mapster\src\Mapster.Tool\Program.cs:line 65
   at CommandLine.ParserResultExtensions.WithParsed[T](ParserResult`1 result, Action`1 action)
   at Mapster.Tool.Program.Main(String[] args) in D:\git\Mapster\src\Mapster.Tool\Program.cs:line 17
System.IO.FileNotFoundException: Could not load file or assembly 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.
File name: 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
System.IO.FileNotFoundException: Could not load file or assembly 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.
File name: 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
System.IO.FileNotFoundException: Could not load file or assembly 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.
File name: 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
System.IO.FileNotFoundException: Could not load file or assembly 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.
File name: 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'