Add a raw_module attribute to #[wasm_bindgen]

This allows subverting the checks and resolution performed by the
`module` attribute added as part of [RFC 6] and has been discussed in #1343.

Closes #1343

[RFC 6]: https://github.com/rustwasm/rfcs/pull/6

crates/shared/src/lib.rs

@@ -28,6 +28,7 @@ macro_rules! shared_api {
         enum ImportModule<'a> {
             None,
             Named(&'a str),
+            RawNamed(&'a str),
             Inline(u32),
         }