Piano: Start working on a desktop piano.

The idea here is to implement a simple synhesizer that allows you to play
music with your keyboard. :^)

It's a huge hack currently but we can improve upon this.

Applications/Piano/main.cpp

@@ -0,0 +1,35 @@
+#include "Music.h"
+#include "PianoWidget.h"
+#include <LibCore/CFile.h>
+#include <LibGUI/GApplication.h>
+#include <LibGUI/GEventLoop.h>
+#include <LibGUI/GWindow.h>
+
+int main(int argc, char** argv)
+{
+    CFile audio("/dev/audio");
+    if (!audio.open(CIODevice::WriteOnly)) {
+        dbgprintf("Can't open audio device: %s", audio.error_string());
+        return 1;
+    }
+
+    GApplication app(argc, argv);
+
+    auto* window = new GWindow;
+    window->set_title("Piano");
+    window->set_rect(100, 100, 512, 512);
+
+    auto* piano_widget = new PianoWidget;
+    window->set_main_widget(piano_widget);
+
+    window->show();
+
+    for (;;) {
+        GEventLoop::current().pump(GEventLoop::WaitMode::PollForEvents);
+        u8 buffer[4096];
+        piano_widget->fill_audio_buffer(buffer, sizeof(buffer));
+        audio.write(buffer, sizeof(buffer));
+    }
+
+    return 0;
+}