Add request scoping samples for AFD

[avanigupta]

Adding some samples to help users set up the right AFD filters according to their application code.

[jimmyca15]

I think we should start with

builder.Configuration.AddAzureAppConfiguration(options =>
{
    options.ConnectAzureFrontDoor(new Uri("{YOUR-AFD-ENDPOINT}"))
            .ConfigureRefresh(refreshOptions =>
            {
                refreshOptions.RegisterAll()
                    .SetRefreshInterval(TimeSpan.FromMinutes(1));
            });
});

Then the next sample can discuss if a Select call is used.

[jimmyca15]

Similarly, with feature flags, I think we should start just with UseFeatureFlags being called, then the following sample could discuss what to do if a feature flag selector is used.

[avanigupta]

Updated, thanks!