add stacking shield

ml/fml40/roles/dts/parts/stacking_shield.py

+from ml.ml40.roles.dts.parts.part import Part
+
+
+class StackingShield(Part):
+    """roles for stacking shield"""
+    def __init__(self, name="", identifier=""):
+        super().__init__(
+            name=name,
+            identifier=identifier)
+