chore: add GUT test framework

addons/gut/scratch/super_funcref.gd

@@ -0,0 +1,21 @@
+extends SceneTree
+
+class SuperClass:
+
+	func print_hello():
+		print('hello')
+
+class  SubClass:
+	extends SuperClass
+
+	func print_hello():
+		print('world')
+
+func _init():
+
+	var sub = SubClass.new()
+	var fref = sub.print_hello
+	print(fref.is_valid())
+	fref.call_func()
+
+	quit()