Fixed example of creating a window with properties

docs/README-migration.md

@@ -1326,7 +1326,7 @@ Rather than iterating over displays using display index, there is a new function
 SDL_CreateWindow() has been simplified and no longer takes a window position. You can use SDL_CreateWindowWithProperties() if you need to set the window position when creating it, e.g.
 ```c
     SDL_PropertiesID props = SDL_CreateProperties();
-    SDL_SetStringProperty(props, title);
+    SDL_SetStringProperty(props, "title", title);
     SDL_SetNumberProperty(props, "x", x);
     SDL_SetNumberProperty(props, "y", y);
     SDL_SetNumberProperty(props, "width", width);