inspect.silhouette: the outline of bodies seen from a view, as a mask (#1743)

Thanks @onembyte.

assets/locales/ja.json

@@ -420,6 +420,7 @@
   "cmd.inspect_interference": "干渉",
   "cmd.inspect_isocurve": "アイソカーブ解析",
   "cmd.inspect_minimum_radius": "最小半径解析",
+  "cmd.inspect_silhouette": "シルエット",
   "cmd.inspect_zebra": "ゼブラ解析",
   "cmd.joint_as_built": "現位置ジョイント",
   "cmd.joint_cam": "カム",