Missing end-of-game experience

Title: The screen freezes after losing the Snake game.

- Steps to Reproduce

Run the snake game: python3 -m freegames.snake

Play the game and wait the end of the game.

- Expected Behavior

At the end of the snake game, I expect a "Game Over" message to be displayed.
A button showing either "Play Again?"  or "Quit?" could be great.
