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

97% of minimum 50% translated source file: 'frontend/src/i18n/en.json'
on 'bg'.

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

frontend/src/i18n/bg.json

@@ -257,7 +257,7 @@
     "preview": "Преглед",
     "settings": "Настройки",
     "signup": "Абониране",
-    "siteSettings": "Site Settings"
+    "siteSettings": "Настройки на сървъра"
   },
   "success": {
     "linkCopied": "Link copied!"