[#6243] Add versionadded directive

Author: wouterj

components/http_foundation/introduction.rst

@@ -128,6 +128,9 @@ has some methods to filter the input values:
 :method:`Symfony\\Component\\HttpFoundation\\ParameterBag::getBoolean`
     Returns the parameter value converted to boolean;
 
+    .. versionadded:: 2.6
+        The ``getBoolean()`` method was introduced in Symfony 2.6.
+
 :method:`Symfony\\Component\\HttpFoundation\\ParameterBag::getDigits`
     Returns the digits of the parameter value;