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.

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