In-game Pause Menu with volume functionality added

While in game you can press ESC button to bring up the Pause Menu. You can change the volume level of the sound with the volume slider and you can return to Main Menu with the appropriate button.

Known bug:

Volume slider in Main Menu settings and volume slider in Pause Menu are working independently. For example - if you set the volume level at 50% from the Main Menu, game will start at 50% volume level, but this will not be visually reflected in Pause Menu volume slider. If you set the volume level at 50% from the Pause Menu volume slider this will not be visually reflected in Main Menu volume slider.