get generate locales disable check for special characters in keys

I have ru_RU.json file as below:
```
{
"Login": "Логин",
"Sign In": "Регистрация",
"Logout": "Выход"
}
```

When I run `get generate locales assets/locales`
I got the error `Special characters are not allowed in key.
key: Sign In`

I thought it is the special feature of GetX that it allows the use of any String as a key by using `"Sing In".tr` extension method.

Please, add the possibility to disable this check or remove it completely.