nost: touch piano mode (#830)

## Link to GitHub Issue or related Pull Request, if one exists
n/a

## Description of change
Touch piano mode. Allows piano keys to be played with the touch screen.
Since the touch screen is still needed for menu navigation (including
during songs) a toggle switch is added so that the user can flip between
navigation mode and piano mode.

The touch targets are pixel-perfect. Don't let the game's piano
animations fool you.

## Testing

src/spice2x/games/nost/touch_mode.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <cstdint>
+#include <windows.h>
+
+#include "touch/native/nativetouchhook.h"
+
+namespace games::nost::touch_mode {
+
+    // nav mode forwards contacts to the game; piano mode converts them into piano keys
+    enum class Mode {
+        Nav,
+        Piano,
+    };
+
+    void enable();
+    void disable();
+    bool enabled();
+
+    Mode current_mode();
+
+    void publish_button_bounds(HWND window, const RECT &client_bounds);
+
+    uint32_t piano_key_state();
+
+    bool filter_native_touch(const nativetouch::NativeTouchEvent &event);
+}