Build 32: options menu & some minor changes

What’s new:

• Added an options menu (press O to toggle it), where you can adjust the master volume, toggle music and change mouse sensitivity
• Experimental “zoom” function (increase/decrease the field of view) with the mouse wheel
• mouse sensitivity is no longer reset when restarting the game with R / gamepad Start
• changed enemy flash implementation, the new one uses color “tint” instead of the brightness effect