Support for `EnumMap`

[`EnumMap`](https://docs.rs/enum-map/latest/enum_map/struct.EnumMap.html) is a crate that exposes an exhaustive hashmap equivalent (backed by an array)

The binding to TS would give a `Record`, as opposed to a `HashMap` which is typebound to a `Partial>`.

Start with the EnumMap documentation and inspect how the existing HashMap binding is handled. Confirm the intended TypeScript representation and identify the relevant binding entry point. Done means EnumMap is supported and produces Record rather than Partial>.

Written by the indexing model from the issue text.