Handle raw bytes for response bodies

[BSchneppe]

other pdks define the response body as a byte array
go - https://github.com/extism/go-pdk/blob/12d6f9af953ad4d386b4171442dacdc49a19b777/extism_pdk.go#L294
dotnet - https://github.com/extism/dotnet-pdk/blob/5bd5ce3fa564bd66428348d684fce199837d8eb5/src/Extism.Pdk/Interop.cs#L493

We should support ArrayBuffers as response bodies too, otherwise we fail for non-utf8
here

js-pdk/crates/core/src/globals.rs

Line 475 in 34837fd

let body = from_utf8(&body).map_err(|e| to_js_error(cx.clone(), anyhow::Error::from(e)))?;

related: #139