Add JSON-FG example with custom geometry

registereditems/geo/json-fg/feature/context.jsonld

@@ -53,7 +53,13 @@
     "links": "rdfs:seeAlso",
     "featureType": "@type",
     "coordRefSys": "http://www.opengis.net/def/glossary/term/CoordinateReferenceSystemCRS",
-    "place": "dct:spatial",
+    "place": {
+      "@id": "dct:spatial",
+      "@context": {
+        "@base": "https://purl.org/geojson/vocab#",
+        "type": "@type"
+      }
+    },
     "time": {
       "@id": "dct:time"
     }

registereditems/geo/json-fg/feature/examples.yaml

@@ -9,3 +9,13 @@
     - language: json
       ref: https://github.com/opengeospatial/ogc-feat-geo-json/raw/main/core/examples/fence.json
       base-uri: https://example.com/json-fg/
+
+- title: Feature with a custom geometry (Arc)
+  content: |
+    This feature follows
+    [the Arc extension](https://github.com/opengeospatial/ogc-feat-geo-json/blob/main/core/examples/extensions/arc.json)
+    for the `place` property.
+  snippets:
+    - language: json
+      base-uri: "https://example.com/json-fg/"
+      ref: examples/custom-geometry.json

registereditems/geo/json-fg/feature/examples/custom-geometry.json

@@ -0,0 +1,26 @@
+{
+  "type": "Feature",
+  "id": "my-space-station",
+  "conformsTo": [
+    "[ogc-json-fg-1-0.2:core]",
+    "[ogc-json-fg-1-0.2:3d]"
+  ],
+  "featureType": "space-station",
+  "time": {
+    "interval": [
+      "2024-05-28T10:33:24Z",
+      ".."
+    ]
+  },
+  "geometry": null,
+  "coordRefSys": "http://www.opengis.net/def/crs/EPSG/0/7415",
+  "place": {
+    "type": "Arc",
+    "coordinates": [
+      81220.15,
+      455113.71,
+      44143.21
+    ]
+  },
+  "properties": null
+}