Do not call BuildServiceProvider in UseFreshMvvm

[ggutschi]

Hi!

The call of BuildServiceProvider in UseFreshMvvm is bad practice (see Microsoft Docs).
For example: Nested constructor injections with singletons won't work.

Best regards

[ggutschi]

As a workaround I'm using

var app = builder.Build();

DependancyService.RegisterServiceProvider(app.Services.GetService<IServiceProvider>());

return app;

instead of

services.UseFreshMvvm();