add self_checkout field to shop=supermarket

Author: Dimitar5555

data/fields/self_checkout.json

@@ -0,0 +1,12 @@
+{
+    "key": "self_checkout",
+    "type": "radio",
+    "strings": {
+        "options": {
+            "yes": "Yes",
+            "only": "Only",
+            "no": "No"
+        }
+    },
+    "label": "Self Checkout"
+}

data/presets/shop/supermarket.json

@@ -1,5 +1,9 @@
 {
     "icon": "maki-grocery",
+    "fields": [
+        "{shop}",
+        "self_checkout"
+    ],
     "moreFields": [
         "{shop}",
         "diet_multi",