[RFC] Lack of support for types none, exn and noexn.

**Is your feature request related to a problem? Please describe.**
N.A

**Describe the solution you'd like**
[exn and noexn](https://webassembly.github.io/spec/core/syntax/types.html#syntax-heaptype)

**Describe alternatives you've considered**
N/A

**Additional context**
N/A
