Added effects manager and two effects to test attached to the player

scene.

scripts/effects/base_effect.gd

@@ -0,0 +1,22 @@
+class_name BaseEffect
+extends Resource
+
+@export var duration: float = 0.5
+
+var _elapsed: float = 0.0
+
+# Called when the effect is applied
+func start(target: Node) -> void:
+    _elapsed = 0.0
+
+# Called every frame (if needed)
+func process(delta: float, target: Node) -> void:
+    _elapsed += delta
+
+# Clean up any changes to the target
+func stop(target: Node) -> void:
+    pass
+
+# Returns true when the effect has run its course
+func is_finished() -> bool:
+    return _elapsed >= duration