Add a Crons sample for aspnetcore with Hangfire

[bruno-garcia]

Hangfire is here:

https://docs.sentry.io/platforms/dotnet/guides/aspnetcore/crons/hangfire/

Note, might be blocked on:

• Crons doesn't work getsentry/sentry-dotnet#3262

Also, onboarding is not yet in-product:

• Crons onboarding for .NET getsentry/sentry#92573