[reference][forms] Adding the radio type

Author: weaverryan

reference/forms/types/radio.rst

@@ -4,4 +4,32 @@
 ``radio`` Field Type
 ====================
 
-See :class:`Symfony\\Component\\Form\\Type\\RadioType`.
+Creates a single radio button. This should always be used for a field that
+has a Boolean value: if the radio button is selected, the field will be set
+to true, if the button is not selected, the value will be set to false.
+
+The ``radio`` type isn't usually used directly. More commonly it's used
+internally by other types such as :doc:`choice</reference/forms/types/choice>`.
+If you want to have a Boolean field, use :doc:`checkbox</reference/forms/types/checkbox>`.
+
+============ ======
+Rendered as ``input`` ``text`` field
+Options ``value``, ``required``, ``label``, ``read_only``, ``error_bubbling``
+Parent type ``field``
+Class :class:`Symfony\\Component\\Form\\Type\\RadioType`
+============ ======
+
+Options
+-------
+
+* ``value`` [type: mixed, default: 1]
+ The value that's actually used as the value for the radio button. This does
+ not affect the value that's set on your object.
+
+.. include:: /reference/forms/types/options/required.rst.inc
+
+.. include:: /reference/forms/types/options/label.rst.inc
+
+.. include:: /reference/forms/types/options/read_only.rst.inc
+
+.. include:: /reference/forms/types/options/error_bubbling.rst.inc