Added CQRS with Minimal API sample

• CQRS flow using Minimal API,
• example how to inject handlers in MediatR'like style to decouple API from handling,
• example of how and where to use C# Records, Nullable Reference Types, etc,
• No Event Sourcing! Using Entity Framework to show that CQRS is not bounded to Event Sourcing or any type of storage,
• No Aggregates! CQRS does not need DDD. Business logic can be handled by handlers.
• 📝 Read more CQRS is simpler than you think with .NET 6 and C# 10

See more in

• code https://github.com/oskardudycz/EventSourcing.NetCore/tree/main/Sample/Warehouse.MinimalAPI
• PR #92.