Fix broken emscripten build

Looks like making the fields public means they
are now exposed in JS so they need wasm_bindgen

I added the attribute on the input side too: the
CI test only needs the output side but it only
makes sense to have it both ways.

src/lib.rs

@@ -332,13 +332,15 @@ pub struct Data {
 /// | wasapi | `QueryPerformanceCounter` |
 /// | asio | `timeGetTime` |
 /// | emscripten | `AudioContext.getOutputTimestamp` |
+#[cfg_attr(target_os = "emscripten", wasm_bindgen)]
 #[derive(Copy, Clone, Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
 pub struct StreamInstant {
     pub secs: i64,
     pub nanos: u32,
 }
 
 /// A timestamp associated with a call to an input stream's data callback.
+#[cfg_attr(target_os = "emscripten", wasm_bindgen)]
 #[derive(Copy, Clone, Debug, Eq, Hash, PartialEq)]
 pub struct InputStreamTimestamp {
     /// The instant the stream's data callback was invoked.
@@ -350,6 +352,7 @@ pub struct InputStreamTimestamp {
 }
 
 /// A timestamp associated with a call to an output stream's data callback.
+#[cfg_attr(target_os = "emscripten", wasm_bindgen)]
 #[derive(Copy, Clone, Debug, Eq, Hash, PartialEq)]
 pub struct OutputStreamTimestamp {
     /// The instant the stream's data callback was invoked.
@@ -361,6 +364,7 @@ pub struct OutputStreamTimestamp {
 }
 
 /// Information relevant to a single call to the user's input stream data callback.
+#[cfg_attr(target_os = "emscripten", wasm_bindgen)]
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct InputCallbackInfo {
     pub timestamp: InputStreamTimestamp,