Add translatable strings to kerb field (#1029)

data/fields/kerb/kerb_barrier.json

@@ -0,0 +1,25 @@
+{
+    "key": "kerb",
+    "type": "combo",
+    "label": "Curb",
+    "strings": {
+        "options": {
+            "flush": {
+                "title": "Flush",
+                "description": "A dropped curb which is level with the surrounding area."
+            },
+            "lowered": {
+                "title": "Lowered",
+                "description": "A dropped curb which can be used by wheelchair users, not higher than a few centimeters."
+            },
+            "raised": {
+                "title": "Raised",
+                "description": "A raised curb which can't easily be used by wheelchair users, higher than a few centimeters."
+            },
+            "rolled": {
+                "title": "Rolled",
+                "description": "A raised curb with a rounded edge which makes it easier to use for cars or bicycles, but not for wheelchairs."
+            }
+        }
+    }
+}