Add Ball class and integrate with Game and Player classes; update Player size and fix Velocity attributes

src/game.py

@@ -1,6 +1,7 @@
 import pygame
 from screen import Screen
 from player import Player
+from ball import Ball
 
 class Game:
     def __init__(self):
@@ -12,7 +13,8 @@ class Game:
 
         self.running = True
 
-        self.player = Player(self.screen_manager)
+        self.player: Player = Player(self.screen_manager)
+        self.ball: Ball = Ball(self.screen_manager, self.player)
 
     def run(self):
         while (self.running):
@@ -27,5 +29,7 @@ class Game:
             dt: float = dt_ms / 1000.0 
 
             self.player.move(dt)
+            self.ball.move(dt)
             self.player.draw()
+            self.ball.draw()
             pygame.display.flip()