minor symfony#11867 [Form] Documented the intl option in TimezoneType (javiereguiluz)

This PR was squashed before being merged into the 4.3 branch (closes symfony#11867).

Discussion
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[Form] Documented the intl option in TimezoneType

This fixes symfony#11503.

Commits
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d96e56e [Form] Documented the intl option in TimezoneType

Author: javiereguiluz

reference/forms/types/timezone.rst

@@ -18,13 +18,15 @@ manually, but then you should just use the ``ChoiceType`` directly.
 | Rendered as | can be various tags (see :ref:`forms-reference-choice-tags`)           |
 +-------------+------------------------------------------------------------------------+
 | Options     | - `input`_                                                             |
+|             | - `intl`_                                                              |
 |             | - `regions`_                                                           |
 +-------------+------------------------------------------------------------------------+
 | Overridden  | - `choices`_                                                           |
 | options     |                                                                        |
 +-------------+------------------------------------------------------------------------+
 | Inherited   | from the :doc:`ChoiceType </reference/forms/types/choice>`             |
 | options     |                                                                        |
+|             | - `choice_translation_domain`_                                         |
 |             | - `expanded`_                                                          |
 |             | - `multiple`_                                                          |
 |             | - `placeholder`_                                                       |
@@ -73,6 +75,28 @@ on your underlying object. Valid values are:
 
     The ``intltimezone`` input type was introduced in Symfony 4.3.
 
+intl
+~~~~
+
+*type**: ``boolean`` **default**: ``false``
+
+.. versionadded:: 4.3
+
+    This option was introduced in Symfony 4.3.
+
+If this option is set to ``true``, the timezone selector will display the
+timezones from the `ICU Project`_ via the :doc:`Intl component </components/intl>`
+instead of the regular PHP timezones.
+
+Although both sets of timezones are pretty similar, only the ones from the Intl
+component can be translated to any language. To do so, set the desired locale
+with the ``choice_translation_locale`` option.
+
+.. note::
+
+    The :doc:`Timezone constraint </reference/constraints/Timezone>` can validate
+    both timezone sets and adapts to the selected set automatically.
+
 regions
 ~~~~~~~
 
@@ -105,6 +129,8 @@ Inherited Options
 
 These options inherit from the :doc:`ChoiceType </reference/forms/types/choice>`:
 
+.. include:: /reference/forms/types/options/choice_translation_domain.rst.inc
+
 .. include:: /reference/forms/types/options/expanded.rst.inc
 
 .. include:: /reference/forms/types/options/multiple.rst.inc
@@ -152,3 +178,5 @@ The actual default value of this option depends on other field options:
 .. include:: /reference/forms/types/options/mapped.rst.inc
 
 .. include:: /reference/forms/types/options/required.rst.inc
+
+.. _`ICU Project`: http://site.icu-project.org/