Ability update

Added skills / abilities:

• Flame sphere: Enemies get knocked back when getting hit (will damage enemies as well in future updates)
• Ice Barrier: Absorb 20 damage (will slow enemies as well in future updates)

Other:

• Added a quick main menu
• Added a temporary game over screen
• Now you can move with WASD or use the mouse (click and hold) like in the original vampire survivors
• Updated background sprites

Soon to be added:

• More abilities
• Adjust fire speed
• Change bullet sprite
• Adjust enemy spawn rate and add different enemies
• Sounds
• More characters
• Skill ranks to level up different abilities
• Add stat focused ranks for move speed, fire rate, shield durability etc
• More levels