Move CSS to Webpacker

app/webpacker/css/mail/all.css

@@ -0,0 +1,11 @@
+/* This file MUST be plain css, as roadie does not seem to be able to handle other file types */
+
+/*
+ * This is a manifest file that'll automatically include all the stylesheets available in this directory
+ * and any sub-directories. You're free to add application-wide styles to this file and they'll appear at
+ * the top of the compiled file, but it's generally better to create a new file per style scope.
+ *
+
+ *= require_self
+ *= require_tree .
+*/