doc: add comments

Exercises on modules with comments.
Playing an MP3.

Author: CodeMayPy

ex021.py

@@ -1,3 +1,4 @@
+#Playing an MP3
 #21- Write a Python program that opens and plays audio from an MP3 file.
 import pygame
 pygame.init()
@@ -7,6 +8,7 @@
 pygame.quit()
 
 
+#Tocando um MP3
 #21: Faça um programa em Python que abra e reproduza o áudio de um arquivo MP3.
 import pygame
 pygame.init()