Serializing custom types into Value, allow named Map instead of Array representation

Being a newcomer to `rmp`, I needed some struggle to understand that I have to enable the `with-serde` feature of the `rmpv` crate for de/serializing data of type `rmpv::Value`. So far so good, e.g. now I can nicely convert a type into a `Value` with `mpv::ext::to_value()`.

However, such `Value`s are always created as `Value::Array`s during serialization and there seems to be no way influencing this behavior. For serialization, usually there's a **pair** of functions where the default serializes into an array (e.g. `rmp_serde::encode::to_vec`) and there's a variant creating a map (e.g. `rmp_serde::encode::to_vec_named`). I cannot see anything similar for values, there's only `to_value()` without `to_value_named()` or anything similar.

Is there any way to serialize a type into a `Value::Map` with the current codebase? Would this require extra development efforts within the library? I even thought of customizing `rmpv::ext::se::Serializer` which seems to cause this behavior, but it's even private in the module.