de: copy lang strings from category

lang/de.json

@@ -15,6 +15,7 @@
     "category:car_maxspeed": "Höchstgeschwindigkeiten",
     "category:car_routes": "Autorouten",
     "category:children": "Einrichtungen für Kinder",
+    "category:climbing": "Klettern",
     "category:coal": "Kohle",
     "category:communication": "Kommunikation",
     "category:construction": "Baustellen",