Updated Use multiple windows (markdown)

Use-multiple-windows.md

@@ -1,3 +1,6 @@
+# NOTE
+**These instructions will not work for Raylib 5.0 or above, they are here for historical purposes only.**
+
 raylib does not support multiple Windows by default, it was designed with simplicity in main and multi-window option was not considered as a core feature.
 
 Fortunately raylib's current design allows adding multi-window support in an easy way, in case some user requires this functionality.