Missing style for info alerts in cart

Noticed that in the shop cart when you save the address info and use an email for an account that already exists, the The alert message shown to inform a user that the email address they entered to the cart is already being used for another account can easily be overseen, as the alert has no background colour. 

I would suggest to add the following to the framework css.

.alert.alert-info {
  background-color: var(--danger-notice-background-color);
  color: var(--danger-notice-text-color);
  border: 1px solid var(--danger-notice-border-color);
}

I am in two minds if I really like the functionality behind this logic. On the one hand, its good that litecart recognizes the returning customer, but on the other hand imagine it was just a typo or the customer just forgot they had an account and had a new address (not realizing that the old address is still in the system - although its not used for the order - but may still confuse) ... would it not be safer to alert the user that this email already has an account attached to it and force the user to log in at that moment or use a different email, instead of doing it for him/her?

Thank you, the intended class is "alert-default". I committed a fix.

If we don't link the order to the account there would be forum threads regarding that. The feature can easily be removed here:
https://github.com/litecart/litecart/blob/2.5.3/public_html/includes/entities/ent_order.inc.php#L210-L221

Excellent, I'll see if the account-link bugs me or not. 
Thanks very much for adding the style :)