What's the status of typed effects?

[welltypedwitch]

No, the initial reasoning was very explicitly about waiting for typed effects

@gasche

The reasoning for this choice [of not including syntax for effect handlers in 5.0] is that we want to give a chance to a type system for effect handlers, but that still need quite a bit more time than the Multicore runtime itself. We don’t want to encourage the ecosystem to rely on untyped effects, if it means a lot of pain upgrading to typed effects later (or risk having to support both).