Update headers from nodejs/node tag v21.0.0 (#34)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
diff --git a/include/js_native_api.h b/include/js_native_api.h
index e06bdc8..0e11eeb 100644
--- a/include/js_native_api.h
+++ b/include/js_native_api.h
@@ -24,7 +24,7 @@
 #ifndef NAPI_EXTERN
 #ifdef _WIN32
 #define NAPI_EXTERN __declspec(dllexport)
-#elif defined(__wasm32__)
+#elif defined(__wasm__)
 #define NAPI_EXTERN                                                            \
   __attribute__((visibility("default")))                                       \
   __attribute__((__import_module__("napi")))
@@ -495,6 +495,7 @@
 
 #endif  // NAPI_VERSION >= 5
 
+
 #if NAPI_VERSION >= 6
 
 // BigInt
diff --git a/include/node_api.h b/include/node_api.h
index 27acc6a..49a23ae 100644
--- a/include/node_api.h
+++ b/include/node_api.h
@@ -1,11 +1,11 @@
 #ifndef SRC_NODE_API_H_
 #define SRC_NODE_API_H_
 
-#ifdef BUILDING_NODE_EXTENSION
+#if defined(BUILDING_NODE_EXTENSION) && !defined(NAPI_EXTERN)
 #ifdef _WIN32
 // Building native addon against node
 #define NAPI_EXTERN __declspec(dllimport)
-#elif defined(__wasm32__)
+#elif defined(__wasm__)
 #define NAPI_EXTERN __attribute__((__import_module__("napi")))
 #endif
 #endif
@@ -17,8 +17,13 @@
 #ifdef _WIN32
 #define NAPI_MODULE_EXPORT __declspec(dllexport)
 #else
+#ifdef __EMSCRIPTEN__
+#define NAPI_MODULE_EXPORT                                                     \
+  __attribute__((visibility("default"))) __attribute__((used))
+#else
 #define NAPI_MODULE_EXPORT __attribute__((visibility("default")))
 #endif
+#endif
 
 #if defined(__GNUC__)
 #define NAPI_NO_RETURN __attribute__((noreturn))
@@ -49,7 +54,7 @@
   NAPI_MODULE_INITIALIZER_X_HELPER(base, version)
 #define NAPI_MODULE_INITIALIZER_X_HELPER(base, version) base##version
 
-#ifdef __wasm32__
+#ifdef __wasm__
 #define NAPI_MODULE_INITIALIZER_BASE napi_register_wasm_v
 #else
 #define NAPI_MODULE_INITIALIZER_BASE napi_register_module_v
@@ -143,7 +148,6 @@
                                                         void** data,
                                                         size_t* length);
 
-#ifndef __wasm32__
 // Methods to manage simple async operations
 NAPI_EXTERN napi_status NAPI_CDECL
 napi_create_async_work(napi_env env,
@@ -159,7 +163,6 @@
                                                          napi_async_work work);
 NAPI_EXTERN napi_status NAPI_CDECL napi_cancel_async_work(napi_env env,
                                                           napi_async_work work);
-#endif  // __wasm32__
 
 // version management
 NAPI_EXTERN napi_status NAPI_CDECL
@@ -197,7 +200,6 @@
 
 #if NAPI_VERSION >= 4
 
-#ifndef __wasm32__
 // Calling into JS from other threads
 NAPI_EXTERN napi_status NAPI_CDECL
 napi_create_threadsafe_function(napi_env env,
@@ -231,7 +233,6 @@
 
 NAPI_EXTERN napi_status NAPI_CDECL
 napi_ref_threadsafe_function(napi_env env, napi_threadsafe_function func);
-#endif  // __wasm32__
 
 #endif  // NAPI_VERSION >= 4