Themes(rolling_stock): add snap to 'railway' function

assets/layers/historic_rolling_stock/historic_rolling_stock.json

@@ -131,7 +131,8 @@
       },
       "tags": [
         "historic=locomotive"
-      ]
+      ],
+      "snapToLayer": ["railway"]
     },
     {
       "title": {
@@ -144,7 +145,9 @@
       },
       "tags": [
         "historic=railway_car"
-      ]
+      ],
+      "snapToLayer": ["railway"]
+
     },
     {
       "title": {
@@ -157,7 +160,9 @@
       },
       "tags": [
         "historic=minecart"
-      ]
+      ],
+      "snapToLayer": ["railway"]
+
     }
   ],
   "tagRenderings": [

assets/layers/railway/railway.json

@@ -0,0 +1,66 @@
+{
+  "id": "railway",
+  "name": {
+    "en": "Railway"
+  },
+  "description": {
+    "en": "Railways and disused railways"
+  },
+  "source": {
+    "osmTags": {
+      "or": [
+        "railway=rail",
+        "railway=tram",
+        "railway=subway",
+        "railway=light_rail",
+
+        "railway=disused",
+
+        "disused:railway=rail",
+        "disused:railway=tram",
+        "disused:railway=subway",
+        "disused:railway=light_rail",
+
+        "abandoned:railway=rail",
+        "abandoned:railway=tram",
+        "abandoned:railway=subway",
+        "abandoned:railway=light_rail"
+      ]
+    }
+  },
+  "minzoom": 14,
+  "title": {
+    "render": {
+      "en": "Railway"
+    },
+    "icon": "./assets/svg/train.svg"
+  },
+  "pointRendering": [
+    {
+      "location": [
+        "point"
+      ],
+      "marker": [
+        {
+          "icon": "circle"
+        }
+      ]
+    }
+  ],
+  "lineRendering": [
+    {
+      "width": 1,
+      "color": "black"
+    }
+  ],
+  "tagRenderings": [
+    "images"
+  ],
+  "allowMove": false,
+  "#": "In first instance to snap historic rolling stock",
+  "snapName": {
+    "en": "railway track"
+  },
+  "credits": "mnalis ALTernative",
+  "credits:uid": 172435
+}

assets/themes/historic_rolling_stock/historic_rolling_stock.json

@@ -18,6 +18,14 @@
   },
   "icon": "./assets/layers/historic_rolling_stock/steam_locomotive.svg",
   "layers": [
-    "historic_rolling_stock"
+    "historic_rolling_stock",
+    {
+      "builtin": "railway",
+      "override": {
+        "name": null,
+        "presets": null,
+        "shownByDefault": false
+      }
+    }
   ]
 }

src/Models/ThemeConfig/Json/LayerConfigJson.ts

@@ -299,7 +299,7 @@ export interface LayerConfigJson {
     /**
      * Advanced option - might be set by the theme compiler
      *
-     * If true, this data will _always_ be loaded, even if the theme is disabled by a filter or hidden.
+     * If true, this data will _always_ be loaded, even if the layer is disabled by a filter or hidden.
      * The opposite of `doNotDownload`
      *
      * question: Should this layer be forcibly loaded?