[Mailer] Update mailer.rst

LiLinen · web-flow · commit ebb0a881f5a7 · 2020-07-03T08:15:59.000+03:00
Add `twig/extra-bundle` to the Markdown Extra Installation Instructions
diff --git a/mailer.rst b/mailer.rst
@@ -526,7 +526,7 @@ several popular libraries):
 .. code-block:: terminal
 
     # instead of league/commonmark, you can also use erusev/parsedown or michelf/php-markdown
-    $ composer require twig/markdown-extra league/commonmark
+    $ composer require twig/extra-bundle twig/markdown-extra league/commonmark
 
 The extension adds a ``markdown_to_html`` filter, which you can use to convert parts or
 the entire email contents from Markdown to HTML:
