add "unleashed" as value for dog tag field

and limit offered values of `dog` field on dog-specific features to just =leashed`/`unleashed`: `no` does generally not make sense on these, and `yes`/`designated` is already implied by the primary tag.

data/fields/dog.json

@@ -6,6 +6,7 @@
         "options": {
             "yes": "Allowed",
             "leashed": "Leashed Only",
+            "unleashed": "Leashes Not Required",
             "no": "Not Allowed"
         }
     },

data/fields/dog_yes.json

@@ -0,0 +1,12 @@
+{
+    "key": "dog",
+    "type": "combo",
+    "label": "{dog}",
+    "options": [
+        "leashed",
+        "unleashed"
+    ],
+    "stringsCrossReference": "{dog}",
+    "autoSuggestions": false,
+    "customValues": false
+}

data/presets/amenity/dog_toilet.json

@@ -10,7 +10,7 @@
     ],
     "moreFields": [
         "{@templates/contact}",
-        "dog",
+        "dog_yes",
         "gnis/feature_id-US",
         "ref"
     ],

data/presets/leisure/dog_park.json

@@ -11,7 +11,7 @@
     "moreFields": [
         "{@templates/contact}",
         "{@templates/internet_access}",
-        "dog",
+        "dog_yes",
         "gnis/feature_id-US",
         "ref"
     ],

interim/source_strings.yaml

@@ -1824,10 +1824,14 @@ en:
           leashed: Leashed Only
           # dog=no
           'no': Not Allowed
+          # dog=unleashed
+          unleashed: Leashes Not Required
           # dog=yes
           'yes': Allowed
         # 'terms: animals,pets'
         terms: '[translate with synonyms or related terms for ''Dogs'', separated by commas]'
+      dog_yes:
+        # dog=*
       door:
         # door=*
         label: Door