feat: markdown in email body for mailing and transactional

composer.json

@@ -22,6 +22,7 @@
         "flagception/flagception-bundle": "^6.0",
         "knplabs/knp-menu-bundle": "^3.2",
         "knplabs/knp-paginator-bundle": "^6.2",
+        "league/commonmark": "^2.10",
         "league/flysystem-bundle": "^3.4",
         "league/flysystem-sftp-v3": "^3.29",
         "league/oauth2-client": "^2.9",