[#3008] Minor tweaks to block_name docs

Author: weaverryan

reference/forms/types/options/block_name.rst.inc

@@ -1,8 +1,8 @@
 block_name
 ~~~~~~~~~~~
 
-**type**: ``string`` **default**: the form's name
+**type**: ``string`` **default**: the form's name (see :ref:`Knowing which block to customize <cookbook-form-customization-sidebar>`)
 
 Allows you to override the block name used to render the form type.
-Useful by example if you have multiple instances of the same form with
-different names so that you need to personalize its rendering.
+Useful for example if you have multiple instances of the same form and you
+need to personalize the rendering of the forms individually.