gd,refacto: added state chart addon and namespace cleanup

addons/godot_state_charts/not_guard.gd

@@ -0,0 +1,18 @@
+@tool
+@icon("not_guard.svg")
+## A guard which is satisfied when the given guard is not satisfied.
+class_name NotGuard
+extends Guard
+
+## The guard that should not be satisfied. When null, this guard is always satisfied.
+@export var guard: Guard
+
+func is_satisfied(context_transition:Transition, context_state:StateChartState) -> bool:
+	if guard == null:
+		return true
+	return not guard.is_satisfied(context_transition, context_state)
+
+func get_supported_trigger_types() -> int:
+	if guard == null:
+		return StateChart.TriggerType.NONE
+	return guard.get_supported_trigger_types()