JA_IsMusicPlaying() added

jail_audio.cpp

@@ -129,6 +129,10 @@ void JA_StopMusic() {
     music.state = JA_MUSIC_STOPPED;
 }
 
+bool JA_IsMusicPlaying() {
+    return music.state == JA_MUSIC_PLAYING;
+}
+
 JA_Sound JA_LoadSound(const char* filename) {
     JA_Sound sound = new JA_Sound_t();
     SDL_AudioSpec wavSpec;