fix vue-i18n message compilation error

src/assets/translations/en.json

@@ -189,7 +189,7 @@
   },
   "login": {
     "title": "Login",
-    "username": "Username (ex: @user:server)",
+    "username": "Username (ex: {'@user:server'})",
     "password": "Enter Password",
     "username_required": "Username is required",
     "password_required": "Password is required",

src/assets/translations/lo.json

@@ -113,7 +113,7 @@
         "title": "ເຂົ້າສູ່ລະບົບ",
         "login": "ເຂົ້າສູ່ລະບົບ",
         "accept_terms": "ຍອມຮັບ",
-        "username": "ຊື່ຜູ້ໃຊ້ (ex: @user:server)",
+        "username": "ຊື່ຜູ້ໃຊ້ (ex: {'@user:server'})",
         "password": "ປ້ອນລະຫັດຜ່ານ",
         "username_required": "ຕ້ອງມີຊື່ຜູ້ໃຊ້",
         "password_required": "ຕ້ອງມີລະຫັດຜ່ານ",

src/assets/translations/my.json

@@ -336,7 +336,7 @@
     },
     "login": {
         "title": "လော့ဂ်အင်ဝင်ရန်",
-        "username": "အသုံးပြုသူအမည် (ex: @user:server)",
+        "username": "အသုံးပြုသူအမည် (ex: {'@user:server'})",
         "password": "စကားဝှက် ရိုက်ထည့်ပါ",
         "username_required": "အသုံးပြုသူအမည် လိုအပ်သည်",
         "password_required": "စကားဝှက် လိုအပ်သည်",

src/assets/translations/pt_BR.json

@@ -195,7 +195,7 @@
     },
     "login": {
         "title": "Entrar",
-        "username": "Nome de usuário (ex: @user:server)",
+        "username": "Nome de usuário (ex: {'@user:server'})",
         "password": "Digite a senha",
         "username_required": "É obrigatório um nome de usuário",
         "password_required": "A senha é obrigatória",

src/assets/translations/pt_PT.json

@@ -318,7 +318,7 @@
     },
     "login": {
         "title": "Entrar",
-        "username": "Nome de utilizador (ex: @user:server)",
+        "username": "Nome de utilizador (ex: {'@user:server'})",
         "password": "Digite a palavra-passe",
         "username_required": "É obrigatório um nome de utilizador",
         "password_required": "A palavra-passe é obrigatória",

src/assets/translations/ro.json

@@ -149,7 +149,7 @@
         "password_required": "Parola este necesară",
         "username_required": "Numele de utilizator este necesar",
         "password": "Introduceți Parola",
-        "username": "Nume utilizator (ex: @user:server)",
+        "username": "Nume utilizator (ex: {'@user:server'})",
         "title": "Autentificare",
         "create_room": "Înregistrare și creare cameră",
         "or": "SAU",