minor symfony#9106 Mentioned how to override each children of a choice type (javiereguiluz)

This PR was squashed before being merged into the 2.7 branch (closes symfony#9106).

Discussion
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Mentioned how to override each children of a choice type

This fixes symfony#4270.

Commits
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f511381 Mentioned how to override each children of a choice type

Author: javiereguiluz

form/create_custom_field_type.rst

@@ -153,6 +153,14 @@ link for details), create a ``shipping_widget`` block to handle this:
             <?php echo $view['form']->renderBlock('choice_widget') ?>
         <?php endif ?>
 
+.. tip::
+
+    You can further customize the template used to render each children of the
+    choice type. The block to override in that case is named "block name" +
+    ``_entry`` + "element name" (``label``, ``errors`` or ``widget``) (e.g. to
+    customize the labels of the children of the Shipping widget you'd need to
+    define ``{% block shipping_entry_label %} ... {% endblock %}``).
+
 .. note::
 
     Make sure the correct widget prefix is used. In this example the name should