Exit and pause event handling and UI button changes. ❗

[JohnCom]

Description

Exit button and pause button in the top right of the game screen to be changed.

Task List

• Remove the exit button and replace with text saying that "esc" button exits the game.
• Add an event for pressing "esc" to exit the game.
• Remove the pause button and replace with text saying that "p" button pauses the game.