feat(demos): add demo for the OSAL (#6182)

Co-authored-by: Gabor Kiss-Vamosi <kisvegabor@gmail.com>

examples/lv_examples.h

@@ -21,6 +21,7 @@ extern "C" {
 #include "layouts/lv_example_layout.h"
 #include "libs/lv_example_libs.h"
 #include "others/lv_example_others.h"
+#include "porting/osal/lv_example_osal.h"
 #include "scroll/lv_example_scroll.h"
 #include "styles/lv_example_style.h"
 #include "widgets/lv_example_widgets.h"