Feature Request: Audio Controls and Pause Menu Keyboard Shortcuts

Currently, there is no way to mute or adjust the volume of game sounds or background music, and the pause menu can only be accessed and navigated using the mouse.
I have a few suggestions:
1. To add a slider for increasing/decreasing volume and a separate mute button too for volume controls.
2. Enable keyboard shortcuts for the pause menu, such as:
Esc to pause/resume the game
R to restart the game from the pause menu
M to exit to the main menu from the pause menu
Also addresses #43