libremidi update to v5.4.3 and added virtual midi out as default

include/libremidi/backends/emscripten/observer.cpp

@@ -4,7 +4,7 @@
 
   #include <cassert>
 
-namespace libremidi
+NAMESPACE_LIBREMIDI
 {
 LIBREMIDI_INLINE observer_emscripten::observer_emscripten(
     observer_configuration&& conf, emscripten_observer_configuration&& apiconf)
@@ -42,7 +42,8 @@ static auto to_port_info(int index, const webmidi_helpers::device_information& d
     -> std::conditional_t<Input, input_port, output_port>
 {
   return {
-      {.client = 0,
+      {.api = libremidi::API::WEBMIDI,
+       .client = 0,
        .port = (uint64_t)index,
        .manufacturer = "",
        .device_name = "",