Document new usage of HTML5_ALLOW_NO_TLD mode. see #47872

Author: guillemfondin

reference/constraints/Email.rst

@@ -109,8 +109,10 @@ This option defines the pattern used to validate the email address. Valid values
 * ``loose`` uses a simple regular expression (just checks that at least one ``@``
   character is present, etc.). This validation is too simple and it's recommended
   to use one of the other modes instead;
-* ``html5`` uses the same regular expression as the `HTML5 email input element`_,
-  making the backend validation consistent with the one provided by browsers;
+* ``html5`` uses pretty the same regular expression as the `HTML5 email input element`_,
+  but also force the usage of tld.
+* ``allow-no-tld`` uses exactly the same regular expression as the `HTML5 email input element`_,
+  making the backend validation consistent with the one provided by browsers.
 * ``strict`` validates the address according to `RFC 5322`_ using the
   `egulias/email-validator`_ library (which is already installed when using
   :doc:`Symfony Mailer </mailer>`; otherwise, you must install it separately).