Small updates and fixes

Player Changes:

- Sliding down walls is now slower

- Jumping has been changed from being able to hold to button presses only

- Players can interact with other players

Enemy Changes:

- Small Critter's health has been reduced by half

- Charger enemy has a windup time and animation before charging

Bug Fixes: 

- Chests no longer eat bullets when open

- Sounds for picking up plasma (the small purple and blue rectangles) has been reduced