Add conceptual article on enhancements to strongly-typed `ILogger` messages

Add conceptual article on enhancements to strongly-typed `ILogger` messages.

- Related to https://github.com/dotnet/runtime/issues/36022
- Conceptual [design-based draft here](https://github.com/dotnet/designs/blob/main/accepted/2021/logging-generator.md)

Collaborating with @maryamariyan on this new article.