document the getEncodings() method of the Request class

Author: xabbuh

components/http_foundation/introduction.rst

@@ -240,7 +240,13 @@ by using the following methods:
   returns the list of accepted languages ordered by descending quality;
 
 * :method:`Symfony\\Component\\HttpFoundation\\Request::getCharsets`:
-  returns the list of accepted charsets ordered by descending quality.
+  returns the list of accepted charsets ordered by descending quality;
+
+* :method:`Symfony\\Component\\HttpFoundation\\Request::getEncodings`:
+  returns the list of accepted encodings in preferable order.
+
+  .. versionadded:: 2.4
+      The ``getEncodings()`` method was added in Symfony 2.4.
 
 .. versionadded:: 2.2
     The :class:`Symfony\\Component\\HttpFoundation\\AcceptHeader` class is new in Symfony 2.2.