Merge branch '4.3' into 4.4

* 4.3:
  Use .yaml instead of .yml
  Update mailer.rst

Author: OskarStark

mailer.rst

@@ -453,7 +453,7 @@ called ``css`` that points to the directory where ``email.css`` lives:
 
         paths:
             # point this wherever your css files live
-            css: '%kernel.project_dir%/assets/css'
+            '%kernel.project_dir%/assets/css': css
 
 .. _mailer-markdown:
 

translation/message_format.rst

@@ -25,9 +25,9 @@ In order to use the ICU Message Format, the :ref:`message domain
 ======================  ===============================
 Normal file name        ICU Message Format filename
 ======================  ===============================
-``messages.en.yml``     ``messages+intl-icu.en.yml``
+``messages.en.yaml``    ``messages+intl-icu.en.yaml``
 ``messages.fr_FR.xlf``  ``messages+intl-icu.fr_FR.xlf``
-``admin.en.yml``        ``admin+intl-icu.en.yml``
+``admin.en.yaml``       ``admin+intl-icu.en.yaml``
 ======================  ===============================
 
 All messages in this file will now be processed by the