feat: add esc_current_scene reserved global (#474)

Co-authored-by: Duncan Brown <duncan@bhs-consultants.com>

addons/escoria-core/ui_library/tools/room_select/room_select.gd

@@ -54,7 +54,12 @@ func _on_button_pressed():
 	# automatic transitions. 
 	# If FORCE_LAST_SCENE_NULL is True when change_scene starts:
 	# - ESC_LAST_SCENE is set to empty
-	escoria.globals_manager.set_global("FORCE_LAST_SCENE_NULL", true, true)
+	escoria.globals_manager.set_global(
+		escoria.room_manager.GLOBAL_FORCE_LAST_SCENE_NULL,
+		true,
+		true
+	)
+
 	var script = escoria.esc_compiler.compile([
 		":room_selector",
 		"change_scene %s" % _options_paths[_selected_id]