Translations update from Weblate

Translations update from Weblate for AlekSIS/AlekSIS-Core-Frontend.

Current translation status:

aleksis/core/frontend/messages/de.json

@@ -193,6 +193,15 @@
     "title": "Gruppe",
     "title_plural": "Gruppen"
   },
+  "holidays": {
+    "create_holiday": "Ferien erstellen",
+    "date_end": "Enddatum",
+    "date_start": "Startdatum",
+    "holiday_name": "Name",
+    "menu_title": "Ferien",
+    "title": "Ferien",
+    "title_plural": "Ferien"
+  },
   "ical_feed": {
     "menu_title": "Kalender-Feeds"
   },