Create/Update assets for version 1.13.2

assets/minecraft/models/block/rail_flat.json

@@ -0,0 +1,15 @@
+{
+    "ambientocclusion": false,
+    "textures": {
+        "particle": "#rail"
+    },
+    "elements": [
+        {   "from": [ 0, 1, 0 ],
+            "to": [ 16, 1, 16 ],
+            "faces": {
+                "down":  { "uv": [ 0, 16, 16,  0 ], "texture": "#rail" },
+                "up":    { "uv": [ 0,  0, 16, 16 ], "texture": "#rail" }
+            }
+        }
+    ]
+}