Async func exports unimplemented in bindgen

[GamePad64]

componentize-js 0.20.0 panics with not yet implemented when a WIT world exports an async function, because the export path in spidermonkey-embedding-splicer/src/bindgen.rs hits todo!() for all three async function kinds:

https://github.com/bytecodealliance/ComponentizeJS/blob/main/crates/spidermonkey-embedding-splicer/src/bindgen.rs#L485-L487

FunctionKind::AsyncFreestanding => todo!(),
FunctionKind::AsyncMethod(_id)  => todo!(),
FunctionKind::AsyncStatic(_id)  => todo!(),

This blocks targeting any WIT world whose exports use async func, including the component-model-async style used by wasmtime 43's component-model-async feature and WASI preview 3 worlds that declare async exports.

[AntonOfTheWoods]

Are there only two of us interested in this?

[GamePad64]

I ended up writing a custom sync-to-async shim component, but I'd like to use native async support, if possible.