Created and added empty ammo shell sprite (#2126)

Resources/Textures/Objects/Weapons/Guns/Ammunition/Casings/ammo_casing.rsi/meta.json

@@ -5,11 +5,15 @@
         "y": 32
     },
     "license": "CC-BY-SA-3.0",
-    "copyright": "Taken from https://github.com/vgstation-coders/vgstation13/blob/0b3ab17dbad632ddf738b63900ef8df1926bba47/icons/obj/ammo.dmi",
+    "copyright": "Taken from https://github.com/vgstation-coders/vgstation13/blob/0b3ab17dbad632ddf738b63900ef8df1926bba47/icons/obj/ammo.dmi, modified by Topy",
     "states": [
         {
-            "name": "s-casing",
+            "name": "base",
+            "directions": 1
+        },
+        {
+            "name": "spent",
             "directions": 1
         }
     ]
-}
+}