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

58% 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

@@ -158,7 +158,7 @@
     "video": "Видео"
   },
   "settings": {
-    "aceEditorTheme": "Ace editor theme",
+    "aceEditorTheme": "Тема на \"Ace редактор\"",
     "admin": "Admin",
     "administrator": "Administrator",
     "allowCommands": "Execute commands",