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/launcher/options.cpp

@@ -3149,6 +3149,21 @@ static const std::vector<OptionDefinition> OPTION_DEFINITIONS = {
         .type = OptionType::Bool,
         .game_name = "Nostalgia",
         .category = "Game Options",
+        .quick_setting_category = "Game",
+    },
+    {
+        // NostalgiaTouchMode
+        .title = "Nostalgia Touch Piano",
+        .name = "nosttouch",
+        .desc =
+            "Allows you to play the piano by touching the screen instead of a controller. "
+            "Use the mode switch button to toggle between interacting with the menu and playing the piano.\n\n"
+            "Velocity sensitivity is not supported. Touch targets will be pixel-perfect aligned with the "
+            "judgement line, key beams, and notes.",
+        .type = OptionType::Bool,
+        .game_name = "Nostalgia",
+        .category = "Game Options",
+        .quick_setting_category = "Game",
     },
     {
         // ForceBackBufferCount