Add docs on NamedAddress::fromString

See symfony/symfony#33086

Author: gisostallenberg

mailer.rst

@@ -158,6 +158,15 @@ Multiple addresses are defined with the ``addXXX()`` methods::
         // ...
     ;
 
+A NamedAddress can be created from a string
+
+    $email = (new Email())
+    // ...
+    ->from(NamedAddress::fromString('Fabien <fabien@example.com>'))
+    //
+    ;
+
+
 Alternatively, you can pass multiple addresses to each method::
 
     $toAddresses = ['foo@example.com', new Address('bar@example.com')];