call an exported start function if it exists

src/run_native.rs

@@ -134,6 +134,10 @@ impl super::Runtime for MicroW8 {
         let end_frame = platform_instance.get_typed_func::<(), (), _>(&mut store, "endFrame")?;
         let update = instance.get_typed_func::<(), (), _>(&mut store, "upd").ok();
 
+        if let Some(start) = instance.get_typed_func::<(), (), _>(&mut store, "start").ok() {
+            start.call(&mut store, ())?;
+        }
+
         let (sound_tx, stream) = if self.disable_audio {
             (None, None)
         } else {

test/start_fn.cwa

@@ -0,0 +1,5 @@
+include "../examples/include/microw8-api.cwa"
+
+export fn start() {
+	printChar('Test');
+}

web/src/microw8.js

@@ -263,6 +263,10 @@ export default function MicroW8(screen, config = {}) {
             window.addEventListener('blur', () => updateVisibility(false), { signal: abortController.signal });
             updateVisibility(document.hasFocus());
 
+            if (instance.exports.start) {
+                instance.exports.start();
+            }
+
             function mainloop() {
                 if (!keepRunning) {
                     return;