wayland: make sure the desktop mode is in the fullscreen mode list

Fixes https://github.com/libsdl-org/SDL/issues/12079

src/video/wayland/SDL_waylandvideo.c

@@ -1025,6 +1025,10 @@ static void display_handle_done(void *data,
     // Expose the unscaled, native resolution if the scale is 1.0 or viewports are available...
     if (internal->scale_factor == 1.0 || video->viewporter) {
         SDL_AddFullscreenDisplayMode(dpy, &native_mode);
+        if (native_mode.w != desktop_mode.w ||
+            native_mode.h != desktop_mode.h) {
+            SDL_AddFullscreenDisplayMode(dpy, &desktop_mode);
+        }
     } else {
         // ...otherwise expose the integer scaled variants of the desktop resolution down to 1.
         int i;