Runes std::collections::HashMap is not accessible from rust extension types

[VorpalBlade]

I want to add a extension function that takes a mapping. So I thought it should take the HashMap from Rune's standard library. Unfortunately that is pub(crate) on the Rust side. What is the best way to do this?

This could either turn into a feature request or a help request (if there is a way to do this and I missed it). I need random access (lookup based on key) into this collection passed by the rune script. I would prefer to not needlessly copy it.