Improve error handling

[jimmyn]

We need to display a human-readable error message to the client on the checkout page

Subtasks

1. Display human-readable error (the error message only) if there is an error that comes from the client. To reproduce this error insert a name with special characters in the Woo checkout form.
2. Hook into the validation form process in Woo and add our own validation rule. WooCommerce_after_checkout_validation Throw a human-readable translatable error if the validation does not pass. "Please enter a valid name. Special characters are not allowed."

[greguly]

~Are there any instructions to reproduce it?~

Names like Ñevzòrov will trigger the error.