Add validation rule: public themes should have a complete translation in english

assets/themes/cafes_and_pubs/cafes_and_pubs.json

@@ -12,6 +12,7 @@
     "hu": "Kávézók és kocsmák"
   },
   "description": {
+    "en": "Pubs and bars",
     "nl": "Cafés, kroegen en drinkgelegenheden"
   },
   "maintainer": "",

assets/themes/food/food.json

@@ -10,7 +10,8 @@
     "hu": "Éttermek és büfék"
   },
   "description": {
-    "nl": "Restaurants en fast food"
+    "nl": "Restaurants en fast food",
+    "en": "Restaurants and fast food"
   },
   "maintainer": "",
   "icon": "./assets/layers/food/restaurant.svg",

assets/themes/fritures/fritures.json

@@ -2,9 +2,11 @@
   "id": "fritures",
   "title": {
     "nl": "Friturenkaart",
+    "en": "Fries shops",
     "fr": "Carte des friteries"
   },
   "description": {
+    "en": "On this map, you'll find your favourite fries shop!",
     "nl": "Op deze kaart vind je je favoriete frituur!"
   },
   "maintainer": "",