add animations module and Explosion Effect (#167)

* Fixed a problem that does not show the remaining life when replaying the game.
* Fixed an issue where an enemy and a player's ship collided and an error occurred. / Fixed an issue where the game could not proceed if the enemy went down the screen.
* add animations module and Explosion Effect

animations.py

@@ -56,4 +56,4 @@ def draw(self, screen):
             if ani.frame == self.sprite.item_count - 1:
                 del self.instances[eid]
             else:
-                ani.frame += 1
+                ani.frame += 1