feat: Translate frontend/src/i18n/en.json in hr

79% of minimum 50% translated source file: 'frontend/src/i18n/en.json'
on 'hr'.

Sync of partially translated files: 
untranslated content is included with an empty translation 
or source language content depending on file format

frontend/src/i18n/hr.json

@@ -229,7 +229,7 @@
     "shareDeleted": "Podjela izbrisana!",
     "singleClick": "Koristi jednostruke klikove za otvaranje datoteka i mapa",
     "themes": {
-      "default": "System default",
+      "default": "Zadano (Sustav)",
       "dark": "Dark",
       "light": "Light",
       "title": "Theme"