minor #13875 [Translation] Document support for calling 'trans' with ICU formatted messages (someonewithpc)

This PR was merged into the 5.2 branch.

Discussion
----------

[Translation] Document support for calling 'trans' with ICU formatted messages

See symfony/symfony#37371

Commits
-------

a490d10 Add documentation for pull #37371

Author: javiereguiluz

translation/message_format.rst

@@ -165,6 +165,21 @@ you to use literal text in the select statements:
 #. Inside this block, ``{organizer_name}`` starts "code" mode again, allowing
    ``organizer_name`` to be processed as variable.
 
+Additionally, it's possible to write the message directly in code::
+
+    $invitation = '{organizer_gender, select,
+                female {{organizer_name} has invited you for her party!}
+                male   {{organizer_name} has invited you for his party!}
+                other  {{organizer_name} have invited you for their party!}
+            }';
+    // prints "Ryan has invited you for his party!"
+    echo $translator->trans($invitation, [
+        'organizer_name' => 'Ryan',
+        'organizer_gender' => 'male',
+    ]);
+
+This can be used to create a wrapper.
+
 .. tip::
 
     While it might seem more logical to only put ``her``, ``his`` or ``their``