Post LD48 update

I took some time after LD48 and updated the game with some polish and features to make it more playable

• Added a main menu and pause menu
• Added a settings menu with sensitivity settings to both the main menu and pause menu
• Added a highscore system at the end of a run, your current run is added in (if it is in the top 10 scores) and shown in green
• Added new UI and sound effects for kill combos
• Added bounce shots, allowing you to bounce shots off walls and around corners to earn a small heal
• Adjusted the taking damage effect and added a slight screenshake
• Adjusted the overall balance, spawn rate, difficulty and scoring across the game, overall should ramp up difficulty a tiny bit slower (to make room for more interesting levels later)
• Some small optimizations to prevent the game slowing down too much as more enemies spawn in deeper floors

Eventually I want to add more interesting levels and variety with enemies, but for now I'm happy with how the game feels as a quick little high score-challenge fps challenge game