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/launcher.cpp

@@ -1786,7 +1786,16 @@ int main_implementation(int argc, char *argv[]) {
             games::iidx::poke::enable();
         }
         if (options[launcher::Options::NostalgiaPoke].is_active()) {
-            games::nost::ENABLE_POKE = TRUE;
+            games::nost::ENABLE_POKE = true;
+        }
+        if (options[launcher::Options::NostalgiaTouchMode].is_active()) {
+            if (overlay::ENABLED) {
+                games::nost::ENABLE_TOUCH_MODE = true;
+            } else {
+                log_warning(
+                    "launcher",
+                    "Nostalgia Touch Mode requires the global overlay; ignoring -nosttouch");
+            }
         }
     }