WASM Host Bindings proposal docs

Hey all,

I don't think these have been shared here (I only just actually learned
that there were published up-to-date proposals).

Draft Reference Types proposal (add an "anyref" type to WASM which
references opaque objects outside WASM):
https://github.com/WebAssembly/reference-types/blob/master/proposals/reference-types/Overview.md

Draft Host Bindings proposal (relies on "anyref" for host binding calls):
https://github.com/WebAssembly/host-bindings/blob/master/proposals/host-
bindings/Overview.md

My understanding from a brief chat with Brad Nelson, just now, is that the
anyref objects can be held directly from WASM - avoiding
host-binding-call-time table lookups (lookups in the WebAssembly.Table).