Add new skills: Double Jump, Ground Pound, Brick Armor, and Brick Shield; implement skill removal signal in SkillManager (#11)

scripts/components/Movement/DoubleJumpAbility.cs

@@ -0,0 +1,46 @@
+using Godot;
+
+namespace Mr.BrickAdventures.scripts.components;
+
+[GlobalClass]
+public partial class DoubleJumpAbility : MovementAbility
+{
+    private bool _hasDoubleJumped = false;
+    private float _jumpVelocity;
+    
+    public override void Initialize(PlayerController controller)
+    {
+        base.Initialize(controller);
+        
+        foreach (var ability in _controller.GetActiveAbilities())
+        {
+            if (ability is VariableJumpAbility jumpAbility)
+            {
+                _jumpVelocity = (2.0f * jumpAbility.JumpHeight) / jumpAbility.JumpTimeToPeak * -1.0f;
+                break;
+            }
+        }
+        
+        if (_jumpVelocity == 0)
+        {
+            _jumpVelocity = -400.0f; 
+        }
+    }
+    
+    public override Vector2 ProcessMovement(Vector2 velocity, double delta)
+    {
+        if (_body.IsOnFloor())
+        {
+            _hasDoubleJumped = false;
+        }
+
+        if (_input.JumpPressed && !_body.IsOnFloor() && !_hasDoubleJumped)
+        {
+            velocity.Y = _jumpVelocity;
+            _controller.EmitSignal(PlayerController.SignalName.JumpInitiated);
+            _hasDoubleJumped = true;
+        }
+
+        return velocity;
+    }
+}