added new todo comment for singelton pattern for bsl (wo only want to allow one object of bsl!)

bsl/nucleo_f042k6/bsl_nucleo_f042k6.hpp

@@ -1,6 +1,8 @@
 #ifndef BSL_NUCLEO_F042K6_H
 #define BSL_NUCLEO_F042K6_H
 
+// TODO: implement bsl as singleton!
+//		 https://stackoverflow.com/questions/1008019/c-singleton-design-pattern
 
 class Nucleo_f042k6
 {