Added GTWeen

GTweensGodot/GTweens/Source/TweenBehaviours/CallbackTweenBehaviour.cs

@@ -0,0 +1,38 @@
+using System;
+using GTweens.Enums;
+
+namespace GTweens.TweenBehaviours
+{
+    public sealed class CallbackTweenBehaviour : TweenBehaviour
+    {
+        readonly Action _action;
+        readonly bool _callIfCompletingInstantly;
+        
+        public CallbackTweenBehaviour(Action action, bool callIfCompletingInstantly)
+        {
+            _action = action;
+            _callIfCompletingInstantly = callIfCompletingInstantly;
+        }
+
+        public override void Start(bool isCompletingInstantly)
+        {
+            bool canCall = !isCompletingInstantly || _callIfCompletingInstantly;
+
+            if (canCall)
+            {
+                _action?.Invoke();
+            }
+
+            MarkFinished();
+        }
+
+        public override void Reset(bool kill, ResetMode loopResetMode)
+        {
+            MarkUnfinished();
+        }
+
+        public override float GetDuration() => 0f;
+        public override float GetElapsed() => 0f;
+        public override bool GetLoopable() => false;
+    }
+}