added resources as a refresher of control flows

Author: UmiKami

exercises/18-The-Beatles/README.es.md

@@ -21,3 +21,5 @@ Este es el coro de una de las canciones más famosas de la banda:
 ## 💡 Pista:
 
 + La frase "let it be" se repite todo el tiempo. Probablemente deberías usar un bucle o loop para eso 😊
+
++ Si necesitas un repaso sobre los loops y/o condicionales, échale un vistazo a esto: https://docs.python.org/es/3/tutorial/controlflow.html

exercises/18-The-Beatles/README.md

@@ -24,4 +24,6 @@ This is the chorus of one of the most famous Beatle songs:
 
 ## 💡 Hint:
 
-+ The words "let it be" repeat all the time, you should probably create a loop for that.
++ The words "let it be" repeat all the time, you should probably create a loop for that.
+
++ If you need a refresher on loops and conditionals, check out this awesome resource: https://docs.python.org/3/tutorial/controlflow.html