adding message about dir structure

Author: weaverryan

src/Resources/doc/index.rst

@@ -4,7 +4,9 @@ The Symfony MakerBundle
 Symfony Maker helps you create empty commands, controllers, form classes,
 tests and more so you can forget about writing boilerplate code. This
 bundle is an alternative to `SensioGeneratorBundle`_ for modern Symfony
-applications and requires using Symfony 3.4 or newer.
+applications and requires using Symfony 3.4 or newer. This bundle
+assumes you're using a standard Symfony 4 directory structure, but many
+commands can generate code into any application.
 
 Installation
 ------------