add gateway for admeme (#17587)

Co-authored-by: deltanedas <@deltanedas:kde.org>

Resources/Textures/Structures/Machines/gateway.rsi/meta.json

@@ -0,0 +1,34 @@
+{
+  "version": 1,
+  "license": "CC-BY-SA-3.0",
+  "copyright": "Taken from tgstation at https://github.com/tgstation/tgstation/blob/1a2b4c66e573cac0e9eb0699b42890b287662de4/icons/obj/machines/gateway.dmi",
+  "size": {
+    "x": 96,
+    "y": 96
+  },
+  "states": [
+    {
+      "name": "frame"
+    },
+    {
+      "name": "on",
+      "delays": [
+        [
+          0.2,
+          0.2,
+          0.2
+        ]
+      ]
+    },
+    {
+      "name": "portal",
+      "delays": [
+        [
+          0.3,
+          0.3,
+          0.3
+        ]
+      ]
+    }
+  ]
+}