add blinking LED example

main.c

@@ -77,9 +77,9 @@ int main(void)
 	io_init(); // initialize IOs
 
 	while (true) { // endless loop for micro-controller
-		/* go to sleep and wait for next interrupt */
-		set_sleep_mode(SLEEP_MODE_IDLE);
-		sleep_mode();
+		/* blinking LED example */
+		led_toggle();
+		_delay_ms(500);
 	}
 	return 0;
 }