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

95% 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

@@ -249,11 +249,11 @@
   "sidebar": {
     "help": "Помощ",
     "hugoNew": "Hugo New",
-    "login": "Login",
-    "logout": "Logout",
-    "myFiles": "My files",
-    "newFile": "New file",
-    "newFolder": "New folder",
+    "login": "Вход",
+    "logout": "Изход",
+    "myFiles": "Моите файлове",
+    "newFile": "Нов файл",
+    "newFolder": "Нова папка",
     "preview": "Preview",
     "settings": "Settings",
     "signup": "Signup",