[Feature] Player's Air State

[rluders]

The state is partially implemented already. This state will deal, in fact, with two sub-states: Fall and Jump.

Describe the solution you'd like

• The jump state can only be used when the player is on the ground;
• The jump should apply an impulse to the player in its vertical axis and keeps its horizontal velocity the same;
• The player should NOT be able to move the player while in the air;
• The player will enter into the fall sub-state when its vertical speed starts to get bigger than zero;